My response: No, LDS Temple practices are remarkably Biblical and provide evidence that important practices of early Christianity have been restored today. The evidence for a restoration from early Christianity is provided in part by Barry Robert Bickmore's excellent book, Restoring the Ancient Church (Ben Lomand, CA: Foundation for Apologetic Information and Research, 1999), now available online at FAIRLDS.org, which is used for much of the following comments for this answer.
While Christ's teachings may have been essentially public before the Crucifixion, shortly before then he told his Apostles that He had "many things" more to teach them that they were not yet able to receive (John 16:12). These teachings undoubtedly include what He taught them during His 40-day ministry after the Resurrection. Of that ministry, all we have recorded is thee statement in Acts 1:1-3 that He showed Himself alive to the apostles after the Crucifixion "by many infallible proofs, being seen of them forty days, and speaking of he things pertaining to the kingdom of God." This ministry was not public and His teachings from then have not been recorded. An extensive Christian tradition exists holding that sacred and secret doctrines were taught during those 40 days.
But even during His mortal ministry, there were teachings that appear to have been given exclusively to the Apostles and not the public at large. Professor Joachim Jeremias in The Eucharistic Words of Jesus (Philadelphia: Fortress Press, 1966, pp. 125-130, as cited by Bickmore, p. 292) explains that Christ gave a variety of esoteric teachings to a very limited audience. For example, predictions of his own death were not given publicly but only to his close disciples (Mark 8:31, 9:31, and 10: 32-34). The same holds for predictions of the end of the world (Mark 13:3). And many teachings were done in enigmatic terms or through parables where the deeper meaning would be available only to those had "ears to hear" (Matt. 9:15) or were "able to receive" (Matt. 19:12). In fact, Jeremias goes on to say that Jesus hinted at secret teachings that would be disclosed later (Matt. 10:27, Mark 4:22), doctrines which Paul may have referred to when he spoke of the "mysteries of God" (1 Cor. 4:1), the "hidden wisdom of God in a mystery" (1 Cor. 2:6-7), or doctrines that some Christians, though they had been Christians for years, were not yet able to bear (1 Cor. 3:2) (see Jeremias, pp. 130-132). Paul's analogy of feeding milk before meat in 1 Cor. 3:2 applies very well to the modern LDS view of the temple as well.
Barry Bickmore provides extensive evidence from early Christianity that hidden truths and mysteries were an important part of Christianity. These esoteric teachings were given to the disciples privately and were kept secret from the world. (See, for example, the comments of Peter in the Clementine Homilies, 19:20 in ANF 8:336, and the Clementine Recognitions 2:4 and 3:1 in ANF 8:98 and 8:117, respectively.) Some knowledge of these secret teachings continued at least into the second century, for Ignatius of Antioch spoke of heavenly things that he feared to disclose to the Roman Christians lest they would not be able to receive it (Romans 9 in ANF 1:104).
The existence of secret teachings and ceremonies in early Christianity was a focal point for attacks by early anti-Christians, as it is today for their modern anti-Mormon counterparts. Celsus, a leading anti-Christian demagogue and agitator (and expert in the tactics so typical of modern anti-Mormons), made strong accusations along these lines. But Origen defended the faith, explaining that Christians weren't the only ones having esoteric doctrines:
But Origen distinguished initiation in the esoteric pagan systems with the esoteric aspects of Christianity in the higher demands of worthiness for the Christian:
In these circumstances, to speak of the Christian doctrine as a secret system, is altogether absurd.But that there should be certain doctrines, not made known to the multitude, which are (revealed) after the exoteric ones have been taught, is not a peculiarity of Christianity alone, but also of philosophic systems, in which certain truths are exoteric and others esoteric.
(Against Celsus, 1:7, in ANF 4:399, as cited by Bickmore, p. 296. )
[W]hoever is pure not only from all defilement, but from what are regarded as the less transgressions, let him be boldly initiated in the mysteries of Jesus, which properly are made known only to the holy and pure. The initiated of Celsus accordingly says, "Let him whose soul is conscious of no evil come." But he who acts as initiator, according to the precepts of Jesus, will say to those who have been purified in heart, "He whose soul has, for a long time, been conscious of no evil, and especially since he yielded himself to the healing of the word, let such an one hear the doctrines which were spoken in private by Jesus to His genuine disciples." Therefore in the comparison which he institutes between the procedure of the initiators into the Grecian mysteries, and the teachers of the doctrine of Jesus, he does not know the difference between inviting the wicked to be healed, and initiating those already purified into the sacred mysteries.There is much of value in the above quote from Origen. We learn that the Christians did have initiation ceremonies involving sacred mysteries taught privately by Christ to the disciples, and that those receiving these mysteries had to live high standards of personal worthiness and do so for a long time. This is remarkably similar to LDS practices. The temple is viewed as a sacred place with knowledge reserved for the pure. Temple recommends require interviews with two priesthood leaders, such as a bishop and a stake president, who determine if the candidate has been living high standards and keeping basic commandments of the Gospel. New converts must wait at least one year prior to being able to receive their Endowment in the temple, and extensive preparation is expected on the part of candidates.
(Against Celsus, 3:60, in ANF 4:488, as cited by Bickmore, p. 296.)
Say, how do anti-Mormons explain the remarkable parallels between early Christian esoteric practices and the modern LDS approach? It's a question worth asking.
By the way, some knowledge of these mysteries persisted into the third and fourth centuries. Even Athanasius spoke of the need to maintain a tradition of secrecy for some aspects of Christianity:
We ought not then to parade the holy mysteries before the uninitiated, lest the heathen in their ignorance deride them, and the Catechumens being over-curious be offended.This sounds like the LDS approach today as well.
(Defense Against the Arians 1:11, in NPNF Series 2, 4:106, as cited by Bickmore, p. 300.)
The word "mysteries" in early Christian writings can refer to ordinances, not just teachings. As used in Greek, it normally referred to the practices of the Greek "mystery religions" that included ceremonies and teachings. As used it the New Testament, it can carry this nuance of rites as well as knowledge (see G.G. Stroumsa, Hidden Wisdom: Esoteric Traditions and the Roots of Christian Mysticism, New York: E.J. Brill, 1996, p. 133, as cited by Bickmore, p. 300).
The LDS Temple is a marvelous, Christ-focused place where great blessings are offered to faithful members of His church. The ceremonies and teachings there are sacred and treated with the respect that the sacred pearls of the Gospel demand. Like the earliest Christians, Latter-day Saints have sacred, private ceremonies offering the most lofty and beautiful aspects of the fullness of the Gospel of Jesus Christ.
Related questions about the LDS Temple are answered on my page, Is the LDS Temple Derived From Masonry?.