User surveys are stressful: they're long, boring and repulse busiest attendees that might be your most important customers.
Ask User is changing it. It asks one question at a time and let your customers to answer with a single click. It results in the high answer rate and keeps your customers happy.
I've been using this tool on https://www.geoscreenshot.com and the user response rate has exceeded other similar tools I've used in the past. Unlike many feedback widgets, the transaction cost for the end user is very minimal (one click) to which I attribute the high conversion rate.
Easy to setup, install, simple and configurable UI.
None so far.