I got one about 6 years ago. I really haven't found as many uses for it as I thought I would. I could blame that on playing mostly bass since I bought it.
I think it is a cool product. Its fun to play a song in standard tuning flick a few switches, play in open E, flick a few more and play black mountainside and then go back to standard tuning. Do realize that when you change tunings you drastically alter the tension on the neck, so it is really hard to just flick the switches and be right on. Sometimes the best it will do is get you close. Close enough to really speed up your tuning between songs. but not perfect.
So I would say if you play slide or a lot of alternate tunings, go for it. Don't get it if you just want dropped D. There are other products for that. I have never used it to drop a whole or half step across the board, so I don't know. But I tink if that was my goal I would save the $150 and buy a capo.