If you use setscissor(0,0,0,0) then you should be able to use a virtual resolution. It will still have black borders dependant on the device resolution/aspect, but you could oversize your screen so it fills the gap. I have used this method with 2 apps now, and although not ideal works ok on all devices I tried so far.
You can also get the devicewidth and height and set your virtual resolution to that. Then when placing you would want to use a percentage to position things. That way it should work on all devices also. the only problem you get that way is scale issues. It worked well for Moon Snaker though. the orientation can also confuse things. Also on phones/tablets with a high res it can slow things down a fair bit if your game is busy.
I must admit I still am always unsure which way to go whenever I start a project regarding the resolution. I have never used the percentage system of AppGameKit though as I find it horrible to use. You would imagine that it would be the best way to work if you knew which ratios you need for all devices.
Marl posted a little code snippet on a thread I posted not long back that may help you with a virtual resolution, and placing stuff down by percentage rather than pixel values.
