Lenovo is coming out with three slate tablets - the Android IdeaPad is already out. There is another one known as the ThinkPad Tablet that will run Android Honeybomb and have n-trig's digital pen as an option. This one is coming out near the end of August. I'm not sure how well it would work with drawing apps, but I'm pretty sure there are some decent apps for Android. But this one will not run Windows programs.
There is a third slate coming later that will run Windows 7. There's really not much information available about this one yet.
If you'd like a windows slate - have you looked at the Fujitsu Q550? The size, weight, and batter life are in line with what you're looking for. Potential drawbacks to that one would be that the Oaktrail processor is weak and the n-trig digitizer may not work as well with photoshop.
The EEE slate would definitely be a great portable photoshop machine, but like you mentioned, the battery life is not so good.