YES! So worth it. I won't lie there are a few issues here and there and some gameplay mechanics aren't for everything but in general they've given the latest AC a refreshing update. The characters and story is touch and go but I think they really nailed the templars well and I am a huge fan of the newest ancestor. Highly recommend it.
Yes... I thought AC2 was okay, but I love AC3 so far. The tree climbing and mobile stealth areas like brush and ferns are amazing for stealth. The graphics are good as well, though admittedly with DX10, ambient occlusion, and a host of other effects, the PC version looks a lot better than the console versions.