A few small points to note,
SDL is a wrapper to the low-level functions very much like DirectX and its only real drawback on the GP32 is that it is dependent on the GamePark SDK currently for providing most of the low-level bits so there is a performance hit (and necessary libC wrapper).
The GP32 SDL port is not a new project, Chui has been working hard on it for well over a year with other projects (http://sdl-gp32.sourceforge.net/). It is currently in its third beta (based on SDL 1.2.7) and is maturing quite nicely. It is still too slow (IMHO) to run any large scale projects (I dust off my SDL GP32 backend for ScummVM every now and then to test this) however it will run most small SDL games quite nicely with a little bit of work, there are already a number of SDL games ported to the GP32 (and DreamCast) by Chui himself that show what it can do..
I used a modified version of the current GP32 SDL port to do my (now discontinued) RAW port and it was at least a viable option for that.
However the GP32 SDL port benefits a lot (speed wise) from being recompiled from source on a newer version of GCC (I use 3.4) as the pre-compiled libraries that are available for download are built with an old version of GCC (with nasty things like interworking enabled etc.). I am testing my versions of Chui’s SDL libs with WinterMutes DevKitArm (GCC 3.4) with a view to packaging them with that if people are interested.