The answer in this case is yes ... mostly. The Guitar Hero franchise has always been about the music and the difficulty curve ... it's fair to say the third installment finds a reasonable groove in these regards.
Considering the torch has been passed to Neversoft (as Harmonix are on with the imminent Rock Band), it's refreshing to see that the developer has mostly stuck to the groundwork laid by the previous two incarnations. The mechanics are the same, holding frets and strumming notes, hammer-ons and pull-offs and so forth. The one note of interest here is the error margin for hitting notes has been relaxed a great deal, so it's easier to pull off a lot of the advanced techniques ...
... which is handy, because there's a hell of a lot more to play. Seasoned GH veterans should have no difficulty with Easy or Normal, but Hard and Expert are much more of a challenge (if you thought Free Bird was tough, try a dose of Metallica's "One" or Dragonforce's "Through The Fire And The Flames"). Be warned that a lot of hard work is needed to get through these difficulties, practice is the key here. Additionally, the tracklist was well chosen and seems to suit the difficulty curve well between the earlier and later levels.
One welcome addition is the more fleshed out Co-op mode. The bass / rhythm parts seem to be more considered and much more technical on later levels, and the addition of a co-op career mode is great, though it would have been better having both online and local play here. The online co-op is limited to quick-play or competitive face-off & battle, but at least it's there, and it's great fun whichever mode you choose.
The other new addition to GHIII is the Battle mode, which requires hitting certain combinations of notes to unlock 'attacks' (such as broken strings, amp overloads) which you can throw at your opponent using the guitar tilt. It's a valiant effort in revising the formula, but in practice it's actually a waste of time, and not particularly engaging.
Despite the few criticisms, this is a solid third in the series, and credit has to be given to Neversoft for not dropping the torch. If you already have GHII, you may find more value in the Solus pack, but the improved wireless Les Paul in the full pack should be considered, especially if you're serious about the co-op mode (where you will need the second guitar).
Play This If You Liked: Guitar Hero II
Worse Than: Being Tom Morello