I'm using 10.5.5 but I don't need big performances I always work with low res leds so no need for big files. In Terms of stability on my side it's perfect.

BTW there was a BIG problem with 10.5 when it come out . then Apple released ( i Think ) 10.5.3 and graphic update and things went allright I don't think now with the lasted there are big differences in terms of performances