I have now played Rock Band for three days on the PS3, and here are my thoughts on the game:
BACKGROUND - I have played GH1, GH2 and GH Rocks the 80s on the PS2 and I am currently playing GHIII on the PS3. I finished GH1 on Expert, and I am down to 1-2 songs on GH2 and GH80 on Expert, and I am currently working through Expert on GHIII. My wife has played all four games, and finished GH1, GH2 and GH80 on Hard and is currently working through Hard on GHIII.
OVERALL - I have enjoyed this game, especially playing with others. I have created two bands - one with my wife and mother-in-law (who is just here for Thanksgiving) and another one with my wife. In the band with my mother-in-law, she sings and my wife and I alternate playing guitar and drums. In the band with my wife, she sings and I play guitar. Right now, we are learning to play the drums on Easy. I must say that after playing 15-20 times I do find that the bass drum pedal is the hardest part of playing the drums. For me personally, I will continue to work and learn how to play it. However, I do agree with those who say it may prevent a "novice" from enjoying the drums. I do wish there was a "party" mode - for friends who have never played - that did not require the bass pedal. In addition, I ready someone's advice and purchase a set of timpani malets at the local music store, and they make less noise when playing that the drum sticks. However, they don't make enough less noise to allow me to play when the wife and child are asleep, so that will limit me to playing the guitar late at night.
INSTRUMENTS - The drums are new and fun to play, and I will enjoy working on the rhythm and learning to play better. Although I will never be a drummer, I do understand better why some people say that if you can play RB drums on Expert then you could play real drums (where playing GH or RB on the guitar has almost nothing to do with playing a real guitar).
The microphone works just fine, and I have even sung a couple of songs myself and have enjoyed it. No problems here.
I would agree with those that have already stated the following - the look of the guitar and the colored buttons are superior to past GH versions of the guitar. However, the strum bar leaves a lot to be desired. I am concerned that it will be difficult to move up to Expert if I am not confident that when I play a note it will register on the strum and in the game.
PROBLEM - Like lots of people, I purchased GHIII on the PS3 in order to get the Les Paul guitar and use it for RB. To be frank, I have not had a chance to need four instuments yet, so this has not been a huge problem. However, if it worked with RB, I would definitely be playing the Les Paul for guitar and using the RB guitar for bass (when needed). I do feel that this has put a black eye on both Harmonix and Sony. Harmonix has "explained" why the Les Paul does not work, but they have not adequately explained why I can not use my old PS2 guitars (with an adapter) or why the Sixaxis does not work as a guitar. It is also another black mark for Sony, as we have another major release where things are great for those with the 360 and those of us with the PS3 are "screwed". Unfortunately, there has been string of these advantages for the 360. As someone who does not play enough to own two systems, I have stayed with Sony and now wish that I did not have these problems - which I would not have with the 360.
DOWNLOADED CONTENT - I have been really pleased with the DLC, and I have already downloaded the Police pack as well as several individual songs. I look forward to future releases and a variety of music.
Overall, I find Rock Band to be a much better experience with a group of people (2 or 3). Playing alone, I would give a slight advantage to GHIII at this time, although that could change if I had a better RB guitar or I could use the Les Paul on RB.
Again, these are just my thoughts...