I just got Hughes Net Gen4. I didn't know about problems with mountain lion before I got it. Lord I hope they fix it soon!
I have a MacBook Pro Retina, osx 10.8.2
IMac osx 10.5.5 and an OLD Dell running windows.
Plugged in direct to Network on the dell near 10 megs down and 1+ up.
Plugged in direct on the IMac a little more that 1.5 meg down and less than 1 meg down.
Wireless.. on BOTH MACS, between 1-2 megs down less than 128K up
I added the "fix" sudo sysctl -w net.inet.tcp.delayed_ack=0 in the terminal and now
Wireless on Macbook Pro is between 5-8 megs download and less than 1 up.