I ran a campaign for 2 or 3 years with Mongoose Traveller--my own setting, though--and it definitely did the job. But I also steered clear of a ton of stuff in the books, including a lot of the tech (I limited the tech levels pretty hard). As an almost OSR-ish core system, I thought it was surprisingly useful and adaptable.
But where it absolutely still shines is in the character generation. Lots of imitators or at least similar lifepath systems, but I have yet to see something on par with Traveler. It was especially great for my campaign, since at some point I had people create a new group of characters to play out a different part of the war, with play alternating between the groups, and later a third team of mutant weirdos (adding house rules for superpower-like abilities was easy), and at one point I even had a couple of players roll up characters for a two-shot (so yeah, I guess that's four total groups of PCs).
With other systems all of those characters would have been a hassle. With Traveler it was just about perfect. Players could let the career paths and events flesh out their characters for them, then we'd fill in the gaps during play.
I'd never say that Traveler is necessarily the best SF game out there, but I think if you keep the tech level on the lower side, it's a hell of a game.