Agree - I have 1600+ text messages running around (too lazy to clean them out).
On first load everything seems to work fine, but then it will apparently "hang" when I open a contact or view all messages (particuarly after the first reset).
ONLY THE FIRST COUPLE OF TIMES THOUGH!
My advice - let it run its course (about 5-10 minutes). After the initial "hiccups" the interface is much smoother (go ahead and open every text messaging menu you can find until the hiccups are gone). You will still see a noticable lag until you clean it out, but it doesn't "hang" anymore. My guess is the happy number is about 300 -- the size of the call history log by default.
(Now where was it in Advanced Configurator to increase that setting.....
)