Folks, I'm experiencing double letter hits as well (examples: like "tthis" or "thiss).
After a lot of investigating and talking with people, I've discovered it's the Android keyboard that is the issue. I reported this to Google here:
Issue 14755 - android - Android keyboard glitch: double-letters - Project Hosting on Google Code and here at the Google Help Forums:
Keyboard registers double-hits randomly... - Google Mobile Help.
Please visit the links and star the report and/or add your own two cents. In the report are also instructions on how to recreate the problem. See if you guys can try.