MUHAHAHAH! I HAVE SEEN IT!!!!
Generally speaking, it's much improved over I and II. So much so that it compares to the original trilogy, although it does have some quite weak parts, which the original trilogy lack entirely (IMO). If I is a 2, II is a 3, and 4-6 are in the 8-10 range, then this is a 6.5 or 7.
The following is truly a spoiler; you have been warned:
One major inconsistancy I noticed is that, according to Leia in ROTJ, she remembers her mother being very kind and beautiful. But since Padme dies right after childbirth, this becomes impossible.
Additionally, what's the deal with Obi-Wan being told to get in touch with Qui-Gon towards the end? Is this the first time the Jedi become aware that dead Jedi can communicate with the rest of the Jedi? It just seemed to me to be a very tacked-on bit, something Lucas just threw in there at the last moment because it hadn't been touched upon at all until that point. Bleh.