import pylab as pl
gives me an unpleasant outfile with the backends GTK, GTKAgg, WXAgg, WX, Agg, GDK and PS. It works fine only with Cairo and GTKCairo. I'm on trunk and Ubuntu 8.04. All backends do fine for png.
It's actually pl.xlabel that kills the eps, if it's replaced by pl.title() everything works again.
Not sure when this problem appeared, but probably not so long ago.