I've ordered Aperture 2.0, but my time with the trial version tells me Aperture is still slow.
It's not the old GPU/rendering story. That's not the problem.
The problem is that Aperture brings up the SBOD (spinning wheel) on very routine operations -- such as deleting images when in "P" (preview) mode. Thirty second timeouts are not uncommon.
These aren't operations that should push any machine. I assume they're related to threading issues with the underlying data storage mechanism.
There's still a lot of rework to be done on Aperture. The 1.0 code base must have been extremely problematic.