Originally Posted by bradyonly

Unlike all of the other fixes that are aimed at the keyboard I did some playing around with "thread_sms.htm" in the windows folder. There's an arguement in there called "count" which calls some function that calculates the characters in the message after every letter. Removing this arguement stops tmail from calculating the character count thus eliminating the keyboard lag.
MAKE SURE YOU BACKUP THREAD_SMS.HTM BEFORE EDITING IN CASE YOU BREAK IT

Summary:
Open Total Commander
Browse to the Windows folder
Look for "thread_sms.htm"
Hit file and go to edit
Scroll down (it's pretty short so it shouldn't be that far) and look for "count" then delete it. It's the only one in there so no need to worry about deleting the wrong one.
Save and restart the phone.

Enjoy!