I just did some quick/simple plots in my module (calling PyQwt) and PyPlot (calling matplotlib). The UI was a little more responsive with qwt, but I couldn't see any major speed improvements, and I was able to zoom/pan in both. In order to reduce fragmentation, I won't move this into a standalone package.
I may, however, give matplotlib another chance and try to figure out whether that can meet my needs (and maybe remember why I switched in the first place).
