This is a good question. Let me check the letter I received two weeks ago when Capcom sent me final review builds of the game. What's this? "Any online review coverage from this build is embargoed until the release of Street Fighter IV, February 17, 2009." /looks at calendar.
So that's that, guys. I've seen a few reviews have gone up, already -- you can search and find them easily online. While it's entirely possible other outlets were given free passes to post their reviews early (print mags or larger sites like IGN, for instance), I'll just be sticking to our original plan here.
If you're wondering (and haven't figured it out yet), I'm just going to recommend that you buy it. And chances are, you've already made up your mind. If you spend $60 tomorrow and you intend on playing human beings (either online or in person), you're not going to be disappointed. Check back tomorrow for more words, some pictures, and a number (if that's what you're looking for).