Yes, its certainly a culmination of everything they've worked on this generation. The gameplay mechanics are ace, can't comment on the story yet, but I love the idea of having three characters. Its also a return to San Andreas, so far from everything we've seen Rockstar may have created the most fully realized game world ever, I think it will be their most beautiful game along with Red Dead Redemption. The three protagonists is really the biggest change however and I'm excited to see where the story takes them.
With that said I'd say Rockstar's best work is Red Dead Redemption, GTA IV, Vice City, San Andreas and even Manhunt. Episodes from Liberty City rocked too. GTA V has not only the potential to be the best GTA in the franchise, but one of the best games this generation. So yeah I'd say this has a really good chance of being their best game.