For what you want... you should probably look at the MacBook 17". There's minimal chance of there being any hardware compatibility issues, as they make the stuff themselves, and you can choose what you want to be put into the machine when you purchase it (thought it might take a few days). The battery is specially made for that model too, to last longer than normal laptop batteries.
It's pretty costly, but you'd probably be better off. It will most definitely run CS4, as Photoshop is made by Apple.
As for the tablet, the Wacom Bamboo Fun is pretty damn good. I own the second gen version (one generation up from Tess'), and it works really well. It's got touch and pen capabilities, and you can turn off the touch feature.