Paid my 80 Euros to upgrade to Live 2.0 a couple of days ago. Awesome new features like different timestretch engines (acoustic guitar tracks actually can be used in Live now), ability to turn those engines off for individual samples, better automatization, etc.
Performance looks to be the same like 1.5 - which means that it still isn't Altivec optimized, and faster on PCs, but the Ableton guys are Mac users themselves and are promising to add this (requiring a bunch of rewrites) for the next upgrade. Anyways, especially with software like Live the performance is nowhere near as important as creativity.