(One of my good friends from Law School has the Pegasus Satellite internet/TV service. The following remarks are based on my using his system for a few hours over the past 6 months or so.)
Latency, Latency, Latency. While the download bandwidth seemed a bit less than my 1.5 Mbps cable modem, the truly frustrating part about using the satellite service is the latency, or turn around time, for requested information.
I don't know if it comes from the system using a time-windowing method, or if there is just a certain delay to be expected in sending a signal ~100,000 miles (Up-back-up-back), but it is certainly noticable compared to my cable modem, my offices 384K DSL, and even a good fast dial-up connection.
Not a lot of info, but I hope it helps.
The speed-of-light delay alone in satellite internet connections is just under half a second (0.47746 seconds, to be precise.) That's a LOT of latency in Internet terms, and that's the ABSOLUTE minimum you can expect with a satellite link -- "I canna' change the laws of physics, Captain!!" Starband sat internet includes software to cache pages locally, reducing the perceived delay, so that may be another consideration.