Right now I believe that GapiDraw is the best platform out there. Fast blits, alpha blits, rotation, scaling, input, etc. The creator of pocket frog has since stopped updating it, yet he helps Sbl out with GapiDraw from time to time.
It has a very simple learning curve, I dont know if you've worked with direct draw, but its nearly identical. Even if you havent had any experience creating applications theres a fairly simple framework setup to get your game running on just about any platform(PocketPC, Desktop,SmartPhone).