I tried a couple of form extension, but no one worked to my utmost satisfaction and the support was mostly bad. Then I installed MooProforms - this is my first Joomla extension I paid for - and I was really surprised, how fast I could make professional looking forms. And I'm sure I have not yet discovered the full potential.
After a few problems (every time my own mistake) the support was very, very quickly and very friendly. I give 10 stars - 5 for the extension and 5 for the support.