It depends on how much signal you have. 3 network 3G, in abergavenny, is as fast as ever you could want it. Even on a good day, where I am, you still have to buffer a video on Utube. I've got to poke the dongle out through a sky light, it won't receive a signal in the caravan. It used to, until I put Kingspan in the walls, so I put it down to the foil on the insulation. Also, tuning the computer a little bit seems to help. I can't remember what I did now, but there are ways of speeding it up.
A dongle does seem sensitive to its environment, and the weather.