Doing a routine update in my desktop, I was surprised to see Qt 4.5 is now in extra! Way to go Arch!
I had a bad start, because all fonts were broken, but after running fc-cache -fv as root and my user it looks ok again.
In fact, it fixes a bug that has been annoying me for a year.
Performance seems to be snappier. That may be a bit subjective, but things like the animations in krunner now are really quick and smooth while before they were jumpy.
And... I can try to make flash work in uRSSus! Yay!
UPDATE: it just started working: