Winpick seems nice, but it doesn’t always return windows to their previous size and place. The most annoying example for me is when the window I keep on the right side of my screen gets moved to the left side and sometimes widened. Other windows are sometimes shortened, though this might not be specific to Winpick — I moved the taskbar panel to the top of the screen, and every Linux desktop I’ve used (except Crunchbang) has had issues properly respecting panels’ space (ie. leaving space for a nonexistent panel or wrongly placing windows under a panel).
I would just avoid using it, but as mentioned in the thread that announced Winpick, it gets triggered during screensaver use (also annoying, but not as much as the other problem). For now I’ve disabled it by commenting out lines 184 & 185 in /usr/local/bin/winfuncs.