First, let me admit that I adore all of the Guitar Hero and Rock Band games. I think it's amazing that you can play along with songs you love, learn real life singing skills, and play with friends and family who don't normally play video games. These series are amazing.
You could complain that they didn't change the gameplay - but really, this is meant as a booster pack of songs. You get the same general characters, the same general gameplay, the same graphics and sound as the previous level. You only get one character to unlock.
You get 8 songs in play mode but to unlock any others you have to go through Career mode. All together you get about 30 songs. I love many of these songs so to me it's worth it.
Now here's the trade-off. With modern Rock Band / Guitar Hero games you can get a new song to add in for about a buck a song. With this one we can assume you probably already had the regular Guitar Hero song. You're getting another 30 songs for MORE than a buck a song - and you're being forced to buy them in a "package" that includes songs you might not like.
Still, the PS2 didn't have a healthy online system like the PS3 or XBox side did so they didn't have the ability to easily add on songs. For PS2 players this really was the only option to add in new songs to their set. It also meant that players who didn't like the music in the original set could buy a "fully functional game" with 30 songs they loved all in one package.
So I definitely understand the complaints of people who owned the regular software and felt they were being ripped off by paying this much for "more songs". I also understand the people who had no interest in buying into the Guitar Hero series until this group of songs came along, and they adored this game. To them this was an awesome deal.
Looking at it from modern times, you can buy this game fairly cheaply and enjoy a wealth of songs you might not find elsewhere. So while I found this well worth it when it first came out, I find it an amazing deal here in current times. Well recommended if you have a PS2 and the guitars!
Of course, if you hate music from the 80s, I'd recommend steering clear :)
Buy Guitar Hero Encore Rocks the 80s from Amazon.com
