What I mean by slow is there's always a lag in update on the widgets. For example, the current time is 1:53pm, but when i unlock my phone the clock widget doesn't update right away and it's still stuck at 1:45pm. When returning to homescreen from an app sometimes the widgets disappear and take awhile to reload. Also sometimes gestures such as swiping down won't work and I have to try it a few times.
I'm using an Xperia Z. I've had this issue with UCCW too back when I was playing around with it. It's ultimately what stopped me from using it and went back to regular android launchers because they were a lot smoother.
Is this how it's suppose to be with custom widgets? Would suck because I really like themer. I do understand themer is still in beta.