I'm astounded Wacom haven't released a pen with pressure-sensitivity built into the pen ,for the ipad, and then just provided patches for all the popular sketch programs on the app store.
If I keep pressing the "swtich screen" button on my wacom pen, eventually it will switch to my sketchbook, then to the postit notes on my desk, then the pad of paper over there...
Does your tablet support the Wacom wintab drivers? Your Photoshop version may only support that while not interfacing well with the drivers from your brand.