I've had some appalling download speeds with 3G although it has improved recently. Programme downloads/Windows updates can take ages or sometimes aren't even worth considering. For example, I needed an SD card software update for my Line 6 Spider Jam amplifier and it would have taken the best part of three hours (assuming it didn't drop off line, as sometimes happens). A friend downloaded it for me on his PC in about thirty minutes.
As soon as my contract expires, I'll be ditching it.
It does its job as a travelling laptop connection, I suppose. I can't recommend it for desktop use.