Not watched it yet, it's sat waiting for me to watch. I'd heard it was crap so haven't rushed in to it.
I'm currently watching Babylon 5. I'm half way through series four, and it's awesome. It's on a par to Farscape for scifi brilliance.
I tend to watch a programme in its entirity if I can, or at least a series at a time. I recently watched lost (also awesome. I know a lot of people say it doesn't make sense and it's a waste of time but I really likeed it. I found the characters very compelling), and next on my list are flashforward, battlestar galactica (the modern one, not the original) and the last two series of spooks.
After that I might get round to stargate.
In case it wasn't clear earlier: FARSCAPE. Download it all and watch it. Brilliant scifi.