This is precisely what I do; DC = 10 + 1/2 CL + ability mod + misc
It's great. Spellcasting needs to be simpler, and targets of spells usually succeed at their saves, especially at high levels, so boosting DCs is hardly a problem. It keeps things like Charm Person useful. There's still multiple DCs to calculate with spell focus and reserve feats and such, but this makes things much easier.
I do it in concert with several other variants, including spell points, a simple spell learning system that also ignores spell level, and multiple ability scores for spellcasters (spell points and spell DCs based on different ability scores).