I use Alt+Tab to quickly switch between applications. It works on the Cosmo, but from time to time, the first press will toggle Caps Lock (which should be Fn+Tab) instead. Subsequent presses will perform Alt+Tab without issue.
When the phone is feeling like doing this, if you Fn+Tab to turn caps lock off, Alt+Tab will turn it back on again (wheeee!).. Bug in the keyboard matrix scanning?