I took me a while to really start to tame mine. It's definitely not one of those pedals that's going to do exactly what you want no matter where to knobs are. You've gotta fight with it a little bit to get it where you want it, but once it's there, it's there. I think the reason it is that way is because it has more options than your standard muff, so you have a larger ball park of "muff/fuzz tone" to play in.
I didn't like mine at first that much either, but I'm nothing but pleased with it now. I run an svt 215, which doesn't have tweeters, and I've circuit bent it for the feedback loop switch. I think it's plenty versatile, but it's also my first venture into fuzz. That being said, I don't use it on its own. I'm not a huge fan of how it sounds by itself. If it's on, I'm running my Pork Loin into it to reclaim some mids, and thicken/warm it up.
Like they've said, a lot of high end is no bueno. I run a low middy/thumpy sound, and I like it that way. Also, it can be touchy to input gain. If you've already made up your mind that you don't like it, by all means pick up another muff. They're cheap and there's about 10 different versions. If you really want to find out what this pedals all about though, sit down and play with the input gain/all the settings and really give it a shot before you move on.