Keith! You've been SO helpful, TYVM. I'm ashamed that I must actually ASK you this—showing my ignorance, nevertheles... the part of your reply where you say;
... You need to log into your router to manage it's settings. If you don't know how to do this, usually you can go into your wireless settings & look for the IP address of your default gateway (typically something like 192.168.1.1 or 192.168.1.254, etc). Then open your browser & type that IP into the address and hit enter. You'll either be presented with the admin page for your router or a login for its user name &f setting available to change. If it's a recent router, you should have to the option to switch from mixed mode (G/N) to just N. You should also see either the QoS or MMS setting that you can disable.
All this having been said, this will only fix your problem while at home. If resetting your iPad's network settings didn't help, I suggest going into an Apple store for service. They will suggest two things, first, to completely restore your iPad. This, of course, you could try at home but it doesn't guarantee to fix the problem and it is a bit of a pain. If you try this, note that you want to do a "clean" install of your iPad when you reconnect it (i.e. don't restore it from a backup in iTunes) or you will just be reloading the corrupted settings from before. The second thing they will suggest is just to swap out your iPad for a new one, which may resolve the problem. Thankfully, I didn't have to go that route, as the reset of the network settings has completely resolved my throughput problems. I've since tested my iPad on several networks and haven't experienced any slowness on them.
Hope this helps!