I just finished the game. I thought it was fantastic. The demos didn't really win me over but the full game certainly did. It's just such a well paced (seriously, that game moves incredibly well) and constantly rewarding experience, with a nice if rather predictable story and some great characters. (including a surprisingly heroic Captain Qwark)
I'm also impressed how there are barely any duds among the many available weapons. When I got the burping frog thingy I fully expected it to be nothing more than a silly gag, but then it turned out to be one of the most potent weapons in the game. It even became my first Level 5 weapon. Heck, even the gun that turns enemies into monkeys is reasonably effective.
A Crack In Time also marks the first time where I was actually looking forward to playing as Clank. The time puzzles were just a ton of fun, especially the 3 extra hard ones. That the Great Clock was artistically stunning certainly helped as well.
I also appreciated all the small touches, like different radio stations in outer space (one song sounds an awful lot like "Eye of the Tiger". Always makes me chuckle and then hum along), or one of the nerdy big-headed aliens whining about how it's like highschool all over again as I accidently hit him with my wrench, or even the banter during the game's credits.
My only real complaints are A: the lack of challenge, and B: too few fully fledged Ratchet levels. Complaining about too few levels is actually a little unfair to be honest. Sure, Tools of Destruction had more Ratchet sections, but then it didn't have the Great Clock, or space exploration with all the smaller celestial bodies. Still, clever additions like the hover boots made A Crack In Time so much more enjoyable for me, and I simply wanted more.
The game felt shorter, even though it really wasn't.