I think it's way overrated personally - it's become a bit of a fad in recent years similar to the bacon craze. It's basically like a bright reddish thick, almost paste-like, hot sauce. It's about the consistency of a jarred pasta sauce like Ragu. It's also got garlic in it as well, though I don't really taste it much. It's hot, but what makes it seem even hotter is how thick it is since it kind of coats your mouth and continues to burn it when you are eating something with it. I can't quite put my finger on why it tastes so different from your more traditional hot sauces like Tapatio or Cholula - it's missing that smokey quality I guess. But it also has a rather unpleasant acidic bitterness to it, that I don't like. If it's diluted into something I don't mind it, but I don't put it on stuff like ketchup like some people do.
Interestingly though, the same company that makes Sriracha also makes two other products - one of them is a more coarsely ground garlic chili paste, which I do kind of like. I mix it with Teriyaki sauce and some honey for a quick "General Tso's Chicken" type sauce. It seriously tastes almost exactly like it.
My current favorite hot sauce would be Tapatio. It's not as vinegary as stuff like Franks Red Hot or Louisiana Hot Sauce, and has a very balanced flavor with a rich smokiness to it, and it's slightly thicker too.