Gusto Head of Product Marketing, Core Portfolio + Platform • 6y
I've used a ton, mostly correlated with my budget :) On $0 budget you can always use Google Forms to send to current / former / prospective customers and export answers to a Sheet.
I like the ease of use of Survey Monkey and GetFeedback for quant.
I like Crayon for competitive analysis on execution. Really Good Emails is an unexpectedly helpful and free way of looking at what companies are doing on email (if you're at a large company).