What do you like or don't like in sci-fi rpg

[3catcircus]

When I want to play space opera, I pull out Star Wars d20. For more sci-fi wierdness, Farscape d20 is the way to go. If I want hard sci-fi, I'll wait for d20 Future to come out in the summer.

Why the insistence on a d20 system?

Space Opera: d6 Star Wars, Star Frontiers, GURPS?
Sci-Fi Weirdness: Gamma World, Twilight:2000 with some of the what-if unofficial addons, Paranoia!, TORG, GURPS, Aftermath, PSI World, Shadowrun?
Hard Sci-Fi: Traveller, GURPS, Space Opera (the game, not the genre - pretty hard, but it does include psionics), Blue Planet?

If you absolutely must have a d20 system, go check out Blood & Space - i've read reviews that indicate that its got parallel mechanics for a Space Opera genre and for a hard sci-fi genre