Traveller20 has a lot of good stuff that I've never seen. I totally dig the +1/4 BAB progressions and the emphasis on social situations, science, and exploration along side combat, but it's unfortunately one of the least used books on my shelf. I was kind of turned-off by the computer rules and all the tables. I think I was spoiled by d20 Mecha (an effects-based vehicle system with very little bookkeeping by the dude who wrote Gurps Vehicles? Sign me up!). One of these days I'll ratchet d20 Mecha's vehicles and Traveller20's starship combat rules together. Though there's still a place for Star Wars-WWII-inspired unrealistic space combat...