I just took the survey. You can just do the line you took most frequent and then skip the rest of the line or buses. I did one subway line and one bus.
Is not that slow, at least when I did it on my laptop, it take a few minutes to load afterward is not too bad. The questions are long and some are repetitive, I guess they try to see if you are consistent with your answer. Hope it will give them some feedback.
Only thing I am surprise is how MTA got a hold of my email, as I never use or signup any MTA services or newsletter.