hopefully it now works in vista in the latest version (2.03.01).
I just tried it on Vista64 SP1. Not quite sure what goes on with it but clicking on help in the Tray Menu would not show the help file. When I did the install I selected "create desktop icon" and there was no icon. I used a restore point after removal at that point.
I was looking for an easy way to set default browser, but it looks like if I want to do anything with URL redirection I'm going to have to bite the bullet and delve into the Registry default browser quagmire(it's even worse on 64 bit with those 3264Wow keys or whatever they are.) Either that or send an email to the author of Browser Chooser. His app sets about a dozen keys when you set it as default browser.
See I have AutoIt3 routine that can get the program path from the active window, so all it would take is associations where the user would set which browser to open when each app tries to open a URL using the default browser. That part of the program would probably take a couple of days. Playing with the registry keys would probably take another week of no fun slogging.
edit: just as a wild guess I'm thinking maybe the help file didn't come up because Vista64 installs 32 bit programs in "C:\Program Files (x86)\" instead of "C:\Program Files\" .. but anyway