A trend you're probably seeing with bad reviews would be people complaining that it was too short or easy. I do have to admit, it's easier than any of of the Guitar Hero games or the other Rock Band games. I rented it and it took me less than three hours to beat story mode on hard while getting five stars on all the songs. Sure, they could have added some more songs but I just don't care. The game was just so good that it doesn't really matter to me. Plus, I think the fact that the difficulty level will make this more accessible to a lot more people.
Another thing I've seen a few complaints about are the graphics. Seriously? I mean, come on it's no Call of Duty but the graphics are on par with any of these types of games. To be honest I think the visuals are where this game shines. Just look at the outfits, the sets where they play, the instruments, and all the fans. It's all very accurate and I think that's simply awesome. Also, the visual interpretations of the Abby Road sessions were spot on.
Now, the audio is great, obviously. Granted, there were a few songs I didn't really like but that's a given for almost anyone. One thing I thought was really cool were some of the small nuances such as the sound bytes in the Abby Road sessions of the actual band members and things like the sound effects of the reel to reel and the audio boards. Very cool.
Overall, this was a very fun game to play and I honestly think it was a much better execution than Rock Band 2. There are plenty of songs to choose from for DLC and I that's one thing that will keep people coming back for more. Even if it doesn't take you long to beat it I think there's still a lot of replay value to this game especially of you're a Beatles fan. Think of it this way, you don't listen to a song you like a few times and then never listen to it again do you. I think this game is worth the retail price and is a must for a Beatles fan.
I should note that I only played through the guitar portion so the vocals and drums might add quite a bit of difficulty to the game and I personally just bought the kit and can't wait to give them a try.