I'm trying to find something decent that works well for the SP4, and I'm curious what you're using - AND WHY. Please don't say "I've got an XYZ brand blah-de-blah" without saying WHY you like it, what you don't like, etc. I'm looking for those who have already ventured out and gotten something, and may not like it (or do like it), but most importantly - WHY. Requirements: Must hold the SP4, and attached keyboard. Have a decent place for the pen - either in a special sleeve/pocket, or some kind of holder. If it's some kind of carrying case - then it must also have the ability to take the power supply.