My experience with ponchos in the Army was good, and actually liked it better than the rain pants and jackets they issued in TA50 (other stuff,not so much!). That said, I use a poncho as my only rain gear when hunting, but realistically our season is so early in the fall, it only gets used to wait out really a really bad downpour.
I am not tall (5'7" on a good day), so I just use gaiters on my lower legs for protection if it is seriously wet getting from point A to point B.
Since ponchos are inexpensive compared to a set of rain pants and jacket, why not get one and try it out? If you don't like it, it will definitely have others uses.
My two cents, your mileage may vary.