A new SDL 1.1 snapshot is available:
http://www.devolution.com/~slouken/SDL/cvs.html
I disabled backing store by default on X11.
Please let me know as soon as you can if this results in a graphics speedup! 
See ya!
-Sam Lantinga (slouken at devolution.com)
Lead Programmer, Loki Entertainment Software–
“Any sufficiently advanced bug is indistinguishable from a feature”
– Rich Kulawiec