I used my friend's satellite connection for several days recently. Obviously different provider and satellite, but presumably the technology is similar. The latency is rather annoying, but I soon learned to just cope with it. It wasn't horrible. I was happy just to have a connection, we were on a large rural property with lots of trees and hills, so it was the only option. The throughput was mostly OK, it was occasionally really slow though. This is for just basic web use. MMPORPGames are definitely out. Std. def streaming worked fine. Hi Def streaming not so much.
Definitely beware of bandwidth overage charges and/or high use throttling policies. I'd say it would be a better service overall than BT's 750K for general internet use. And if BT is like American phone co.s, you'll more likely get closer to 500K actual throughput based on that claim!
Your experience will largely depend on your usage habits, what connection speed you're used to, and your expectations. My regular connection is on the slow side (1 - 1.5M), so satellite was OK comparably. If you're used to a faster connection, it will seem very poky.