Have you ever used Lazarus? I'm curious how it compares to Delphi specifically for GUI development. From a rapid GUI development standpoint, they seem to be the only game in town aside from VisualBasic.
I used it for a small project where I needed a quick way to plot some lab data. I chose Lazarus because these data needed to be displayed on all the computers in our lab, including a few Windows machines.
I was amazed when the program I developed on Linux compiled and ran flawlessly on Windows at the first attempt!