I never used the standard HTC msg app long enough to know I use handcent. But I came from an Eris and I used it while on it....it rarely if ever lagged.

 

mines not laggy.., maybe u have too many messages?

 

mine gets laggy if the thread is too long, but I switched the handecent and it seems to load much quicker for whatever reason.

 

Mines only lags on the threads that have over 700 sms's. The "Loading" screen takes a good 10-15 secs

 

You have too many messages for the stock app. However, I use Handcent and even with thousands of texts logged, there is little to no lag. When I open the stock app, it lags bad.