If you browse the web or send emails while laying down (say in bed) it can be very frustrating that your phone switches to lanscape when you want it to stay in portrait mode. Execute the following reg tweak so that the phone will only rotate to landscape if it is tilted over 60 degrees as opposed to 35 degrees.
HKLM\Software\HTC\HTCSensor\GSensor\LandscapeAngle Threshold and change from
35 to
60.
From
http://forum.xda-developers.com/showthread.php?t=583638