The smart render sure does speed things up. When it kicks in you can see the frame counter start to jump by 50's and 100's. But the rendering of the parts to be re compressed (dissolves, transitions... etc) is a HECK of a lot slower than V7!
I think I am starting to notice this too... I am rendering on a P4 3.2 XP machine 2 hours of HDV footage with maybe 50% at most of the clips with a color corrector filter. Rendering to m2t 60i I am at 12 hrs with 4.5 hours reported as left to go. 8 bit render as well... I don't remember them taking that long, but I'll have to test it on the quad Vista and see.
The slowdown is not related to smartrender being on or off; it's attributable to the 32bit video processing. In 8bit, it's in every aspect as fast as it used to be in V7; switch 32bit and my CPU isn't even 40% loaded! Certainly unoptimized code there.