I've only used it once and in a pretty low dosage of 150mg just to complement my test. Overall i won't say it's bad and honestly for me it was the most 4 relaxed months regarding dialing in e2. It kept me stable in a sweet spot while with AI's i'm still kinda all over the place, haven't found a sweet spot.
As far as worth it or not, i'm gonna say this. If you're relatively new to gear and assuming you're not old enough, i'd say not bother with it. They say it's mild, easy on the body etc.. Why spent 4 bulking cycles to add a X amount of muscle mass with a mild compount that costs enough money, it's low on concentration and sometimes gives you PIP if you can put the same amount of muscle mass in 2 or 3 bulking cycles with just high test or test+nandrolone or test+EQ? Many guys talk about side effects, but some guys really handle NPP or EQ very very well. What if you're one of them?
I've seen guys in 1gr of test + 1gr of deca and they're fine. Some start crying or get a noodle dick from 200mg, i believe it worth trying it.
Primo will always be a great compound for older guys or more sensitive to stronger compound sides. Or you can simply use it for physique purposes since it gives a nice look but AFTER you reach a good level of muscle mass. If you're in a point with a bodyweight you're satisfied and you just want to improve your look, then i think it's a very good choice.
If you're starting now taking gear, especially with those low test high primo or mast cycles, i believe you just leave gains in the tank. And honestly if you need 700mg total of test and npp or EQ to make some good progress while in cycles with primo or mast you push up to 1gr since they're "safe", are they actually that safe? Because everyone's lipids are going to hell with high DHT's anyways.
That's just my personal view of things, at least for now, that's how i'm thinking it..When i become more experienced i may reconsider, or maybe not.