I've never used Survey Monkey before(Not to my Knowledge or Memory anyway). It is quite convenient to use something like it cause of course. It's a Survey and depending on what it's about, you could get some interesting results.
I should mention that's quite cool that you're going to do a Survey for your Blog. Good luck with it!
Personally? No. Most surveys I have done of my userbase, I prefer to be able to have one on one conversations in private, than use a survey site, where the person filling the survey out might not provide their username or give an appropriate survey response. One of the last surveys I participated in on a forum I help run, the survey was a mess, because the survey was being filled out by people who had an agenda, which involved hiding identities and trying to get the owner and other administration to boot people from staff, so that those users complaining could some how get themselves or someone else who will do what they want, into favored staff positions.