It's not terribly slow, but it's slow. I use Labels as the widgets, so it should be faster, in theory... The most annoying part is turning it off - it takes 5 seconds to close the application (hmm... sending kill messages to 200+ windows).

Anyway, I implemented a table with a Canvas, it works nicely and is faster. I needed another Canvas for the headings though, as I wanted them to be un-scrollable.