How to choose the right feedback tool for your needs? You have to consider several factors.
First, you have to take into account if the feedback tool in question has all the features you need. While there are many single-use solutions available, a really good feedback tool should enable you to collect feedback through multiple channels, automatically send surveys and so on.
Second, consider the price. While collecting feedback is certainly an important part of improving your business, it should not be prohibitively expensive. A sliding scale of prices is perfect - it allows you to add new functionality at any point in time, without the need to migrate to a new system.
Third - think about collecting feedback both during and after the experience you're trying to improve. Something like a site widget is a good way to provide an unobtrusive, but always visible feedback prompt. Automated e-mail surveys and rating boxes in e-mail footers are also a must.