http://bradfitz.com/android/K9Sms.apk
It's a lot faster to scroll around and stuff now. No more repetitive, uncached, blocking SQL queries in the UI thread when each list items comes in/out of view.
With permission from Jesse Vincent, I named it after k9mail, as it's in a similar spirit. We'll probably put it in k9mail's svn repo until all the changes get merged into mainline. Consider this a temporary, experimental fork.