As reported in the screen protector threads I am using a Vikuiti DCQ-160 screen protector. The first one was slighlty too big and needed cutting. New replacement is perfect size. Seems like very good protection, easy to apply and reapply without residue, has proper holes for all the sensors, lets the screen shine through well and works great with finger and stylus.

I use a screen protector mostly because of frequent stylus use. I don't want to worry about scratching the screen when madly stylusing around.

For overall protection I use the black sock (yellow inside) from Nokia that fits well over many Nokia models including the N900.