I do, sometimes. I usually use Google forms, because the data is in an easy to see format. Plus, I'll remember what service I used instead of some random bum of the edge of the internet world startup that disappears in three months. My polls have always been extremely targeted. Once, I tested out a different CDN and polled my users about their region & how the speed of images were to them.
Fun fact, CDN77 loads faster in Europe, according to my users. But, MaxCDN is much faster in Africa, Middle East, Hong Kong, Japan, and Australia. MaxCDN was also faster on the East Coast and in Texas. CDN77 was faster in California. I was going to try out Beluga, but, it took them like 4 months to reply to my support email so I ditched them. 4 months to reply to a potential customer, not good. No wonder they have to spam ads everywhere.
I also polled users when I did a server move, to see how long it took for upload functionality to come back.
MaxCDN is starting to get really expensive