I also use Jotform (which is actually free if you don't have many submissions per month), and find them pretty effortless in terms of integration. However they have been known to go offline occasionally and I have found their facility to pass form data onto a Google Drive spreadsheet to be somewhat flawed. For the simple processing of forms though they are pretty reliable.

I have also recently downloaded Formoid (http://formoid.com/), which is a beta project by the guy or guys who make WOW Slider and CSS3 Menus etc. I haven't actually tried using it with XDP yet since I haven't had a project since I got it that required a form but it looks like it ought to work OK.