VWO is awesome, really quick and easy to set up tests. And the support is incredible. The few times I've emailed the support address I've had a reply from Paras in less than an hour, I'm beginning to wonder if he ever sleeps :)

The only complaint I did have about VWO is that there was no way to make a variation that touched multiple parts of a page. But apparently you now can! (last item on the list in the article)