Earlier quoted context omitted.
It's a well designed win32 application, designed to the portable as far as windows applications go. I just don't get the hate on PuTTY.
It's a functional application. It's not well designed. It's not "portable". The hate is because it is so mediocre it's insulting to anyone who uses Windows and has to suffer through it. If you prefer it, that's fine, but some people expect a bit more from their tools than merely being "functional" no matter how ugly.
Well designed can refer to more than just the interface. It meets historical windows human interface guidelines too.
I'd also suggest that its an open source project, and could be forked, with a new UI wrapped around the existing pretty good terminal emulation.