I am currently reading Sidney H. Griffith's The Bible in Arabic, which devotes a substantial portion of its total pages to investigating the Qur'an as it relates to the Bible, as the Qur'an is in some sense the antecedent to the Arabic Bible translations that would come out of the preexisting Christian and Jewish communities of Arabia in the wake of the arrival of the Qur'an and the religion built around it. Griffith makes the somewhat atypical claim (which I'm not sure I'm buying, but am trying to suspend judgment on, since I love Griffith's work) that the anomalies we find in the Qur'an with regard to its presentation of Christian and Jewish doctrine do not reflect the influence of gnostic or otherwise heretical forms of these religions, but actually reflect some level of understanding and concord with the mainstream positions of the preexisting communions found in Arabia in Muhammad's day, like the Miaphysite Orthodox and the Nestorians (of course, most people would say that one or both of these communions are themselves heretical, but I think Griffith's point of view is that whatever the Qur'an inherited from Christians wasn't from Ebionites or others like that, in contradiction of the position of many scholars who have investigated this topic who say exactly that).
My point of view is that any such apologies for the Qur'an via the Bible (such as are popular among Muslims themselves, too) are bound to fail, because even if the Qur'an does ultimately draw its inspiration from "mainstream" Christian sects in so far as its recall of Biblical stories and figures are concerned, what it makes of them after mutilating those stories and persons is largely unrecognizable. Griffith writes repeatedly how this or that story or personality is obviously rooted in some form of Biblical recall, but does not match up with Christian or Jewish traditions regarding the same (let alone quote any Biblical passage word for word, save one possible exception) because it is consciously changed to fit the Qur'ans "distinctive prophetology", or its view of itself as "corrective" to the errors of the Christians or Jews. Well excuse me, but that strikes me as a bit bizarre; sort of like saying "Mormons aren't heretics; they're just twisting the Bible to fit their own 'distinctive theology'" or something similar. The Qur'an, and hence the religion that is built around it, fails quite simply because it is not what it says it is: It is not the word of God/Allah (and, as a corollary, Muhammad is not the messenger of God/Allah, his "revelation" is false, etc). And we can know that it is not what it says it is because it fails in its own stated goals to serve as "reminder" of what came before (since it doesn't match what came before, but instead only twists it around), and to bring people back to the true religion that has apparently been corrupted by the preexisting Christians and Jews (since Muslims can never show where the supposed corruption took place, only point to areas where the Bible contradicts the Qur'an as though that is self-evidently the same thing). It is a bit of a Goldilocks religion (...but Muhammad's revelation was juuuust right), and I have always gotten a sense that there is some kind of "me too"-ism in its approach to other religions: The Jews have their prophets and patriarchs and the Christians theirs, but who ever thought that there should be a prophet from among the Arabs, or took to heart what he claims to have brought forth because God has revealed this new thing in 'clear Arabic'? (as the Qur'an congratulates itself for being...well whoopty-freaking-doo...er, excuse me...alhamdulilah...)
Some people, even Orthodox people, have said that the Qur'an and Islam are essentially no different than Christianity in this regard, as Christianity sees itself as the fulfillment of Judaism in some sense. I am not sympathetic to this view for at least a few reasons:
(1) At the time of Christ (and, in the Jews' view, of course also after Him), there was a preexisting belief in the coming of a Messiah. For Christians, Jesus is that Messiah as well as being the Son of God. In contrast, by the time of Muhammad, for at least the Christians the Messiah had already come and it had been accepted for centuries that there would be no other Messiah, nor any new prophets or new revelations after the deaths of the Apostles. So Muhammad is out. (For the Jews, not being one myself I can only say that as far as I know they do not accept Muhammad as a prophet, nor do they agree with the Qur'ans contention that somehow Jesus is the Messiah, so he would appear to be a failure in that religion, as well.)
(2) Christianity does not seek to strength itself by claiming any textual corruption on the part of the Jews, as we do indeed accept their scripture as our scripture (even though our canons and versions of accepted books differ for historical reasons). Rather, related to Christ's divinity and the authority invested in His interpretation as the final and only correct interpretation of whatever matter is at hand ("You have heard it said..., but I say unto you..."), we say that the Jews are mistaken in rejecting Him and His commands. This difference might seem subtle (e.g., Muslims or others could respond "Well, Christians and Jews are wrong in rejecting Muhammad and the commands brought in the Qur'an, too!"), but it is quite important. It lays in the source of authority by which someone can claim that they should be followed, as we say that Muhammad brought a new revelation that contradicts what was known before, and cited as his authority revelations from "God" which no one else ever saw or was allowed to question. By contrast, at least for Christians, as Jesus is God, that's the only authority He needs. Muhammad, not being God, cannot claim the same authority.
For all these reasons and more, I find Islam very flawed, and have no trouble at all rejecting it. It only even gets brought up in the context of comparison to Christianity or Judaism because it has falsely wedged itself into some sort of vague "Abrahamic" family (com'on...even Christians and Jews share some of the same texts, and their rituals share some common ancestry), but at its roots it is something else, bringing a new revelation that is not believed by any preexisting religion (all the while claiming to be in conformity with them), from a prophet who nobody asked for, to a marginal people who, were it not for their false prophet and the religion he and his successors forced upon the world (including Arabia proper), would not have much in the way of non-regional accomplishments, literary culture, etc. No wonder Muslims insist that the Qur'an is Muhammad's miracle. I don't buy it. Islam is bunk.