I bought DMAA and have used it pre-workout for maybe a year or so. Not non-stop, just on and off.
I find that you get tolerant to it really quickly, for me after a week or so I have to up it or stop using it. 25mg is a nice boost, 50mg can feel like mild doses of illegals. You need to take it with caffeine though for these effects. It's like Pseudoephedrine in that way.
I'd suggest trying it, but make sure if you get caps to get 25mg doses as I could definitely see 50mg being too much for a lot of people to start off of. Also make sure it DMAA, and not Geranium. They're not the same. One is a plant derived (tincture I think) version with a variable amount of the active chemical, the other is just the active chemical (DMAA).
Personally I've found my best sessions have generally been when using this stuff, before I've built a tolerance.