I'm seeing improvement as well. On one particular image from a client, that was completely blacking out the monitor and doing a redraw in about 20 seconds, is now only showing (not responding) for a short time! LOL
This is a pretty extreme case, however with multiple paintbrush masks, multiple gradients, loads of "healed" sensor dirt, curves adjustments, fringe corrections, color bending, and some pretty serious noise reduction, sharpening, etc. It has to be the poster child for a difficult, heavily messed with image file.
On most of my own a900 RAW files (imported fresh for testing) it seems usable, if not quick, which I'll take! Slider responsiveness still lags a tiny bit, but at least gives me a sense of "where I am" in the adjustment rather than a "surprise!" when it catches up.
Good on you, Adobe! I know this couldn't have been much fun on the release of such wonderful and powerful changes, to have to deal with this issue.