Just from a bit of wiki reading, it sounds potentially dangerous, there is a pretty high incidence of side effects, and it has been pulled from a number of countries for causing heart attacks and "sudden death". It's an SNRI with very light DRI properties. Personally I wouldn't touch it. It doesn't sound all that pleasant. It's used as an appetite suppressant for weight loss.
I never tried phentramine, I do have some experience with sibutramine. It's nothing to get excited about. The only real use I found for it was offsetting the HBWR induced laziness and enjoying the outdoors a bit more. I wouldn't waste the time/money on what's essentially a dud of an appetite suppressant that does little to nothing to even suppress ones appetite.
I was taking it forever, trying to renew script. Doesn't seem to be one many take for recreational use. Works well for weight loss but really was most useful for hangovers and waking up in the morning.