I would HIGHLY recommend trying a Big Bang if you've never done so before, or you're waffling whether or not to sign up. Why? Because if you're in need of a boost, stuck in a rut, or using a searchlight to find your Muses, this could be your solution!
Now, I would recommend that you at least have a plot idea before signing up, and perhaps do a quick outline to see if you can reach the minimum, but I know I'm juggling two Big Bangs right now and finished my first, and it's really helping my output and creativity! So if you have an old idea lying around you've wanted to do for years and would prefer a more relaxed schedule than NaNoWriMo and a lesser word count, I would say go for it! You can always drop out and try again, because sometimes the time isn't right, but you'll never know unless you try! ;)