Having a UserVoice widget on your site suggests that you don't have confidence in your own product. I recognize they have slightly different purposes, but the general thrust of both is "give us feedback" ... so having their widget feels like it's undermining your offering.
If when creating your own multiple choice questions, if you select the "show text box upon selection" checkbox, I think you should be able to define text for a label that appears next to the textbox (that would contain something like "Please explain", or "Tell us more").
Looks fantastic, immediately I want to use it on my sites.
I have looked for a live demo on your site but can't see one.
Don't just go for the hip startup crowd. Create a landing page specifically for Travel agents, with questions and examples relevant to that industry. Do they same for real estate agents.
I like it. I've used wufoo for surveys before and have had mixed results. I think being able to embed specific questions on the site is a great idea.
The site looks good. Pricing feels ok to me. I think the biggest competition (around here anyway) is people rolling their own. I still see a lot of use for this. The market is big enough you should do well.
I think this is nice, especially w/ customizable questions. But let me play devil's advocate and ask: what is PopFeedback going to do for me that KISSmetrics or another couldn't?
Well, we actually made it because we wanted to use KissInsights on our other startup SocialBlaze, but it was too expensive (we're bootstrapped). So we made our own for ourselves and decided to open it up and charge a price we would have paid instead of making it.
Honestly, right now it's just price (and even free surveys are customizable) and the fact that you can setup a follow up action such as asking for an email, asking to follow you on twitter, or like you on facebook. So if the user is already engaged enough to answer the question, he/she is more likely to give you their email or follow you on twitter/facebook. But we have a few other ideas on what to add to make this even more useful and differentiate ourselves better.