I'm amazed at the number of you that have your own scan tools!
I'll be Mr. Practical here and suggest to my buddy David that you ask for something else for Christmas.
IMNSHO OBD II is a joke. I have run across many OBD 2 codes (aka PO####) that will cover several factory codes (aka P####) leaving you to scratch your head. In addition to what Steve stated about not being to check other systems on your car keep in mind that just because there is a fault code stored for a particular component doesn't always mean that component is at fault. IMO there are too many varibles that OBD 2 just doesn't cover.
I have used both OBD2 and factory scan equipment (HHT at that time). I'll take the factory scan equipment any day.
Is your "CHECK ENGINE" MIL coming on that much?