UI is important because it affects the feelings, the emotions, and the mood
of your users. If the UI is wrong and the user feels like they can't control
your software, they literally won't be happy and they'll blame it on your
software. If the UI is smart and things work the way the user expected them
to work, they will be cheerful as they manage to accomplish small goals.
Hey! I ripped a CD! It just worked! Nice software! Wooooooooooo!
Recently,I found a good UI resource software HelloUI, it collects some very
good UI work.
Serious recommend to you:
Hello UI introduction URL
http://www.qwerks.com/product.asp?ProductID=6873