It is what many followers of Islam take it to be, is it not.
No its not. The sayings and stories concerning the life of Muhammed are an entirely seperate body of work, namely the hadiths. These are a huge subject in and of themselves, but as a brief summary of the position that (most) interpretations of (part of the problem here is that it is not possible to accuratly summarise complex positions held by millions worldwide into a few pithy lines) Islamic theology takes is that The Qu'ran was revealed to Muhammed by Gabriel over a period of some years, and that it is the original word of God.
Muhammed himself, whilst an object of love and to a certain extent veneration, is not an object of worship per se, he did not perform miracles, claim to be anything like the son of God etc etc or (usually) claim to be anything else other than the revealer of the word of god. If you look at the call to prayer issued from mosques, it identifies Muhammed as the messenger of god, nothing more, and prayers tend to be (am not sure if they all are, but I can't think of an example where they are not) directed at god, not Muhammed. Its a complicated one, but it is fair to say that, in general, Muhammed is not worshipped, Allah is.
Oh, and صلى الله عليه وسلم


Idolatry is against tevhid, sure, and it is probably shirk, but it ain't blasphemy. Blasphemy would be speaking to defame/harm/deny the prophets/the Qur'an etc.