It depends on which 'bits' of traveller you're using; basic rules (fine), ships (cool but physics is having a quite cry in the corner at some of the details), trade (errr....), psionics, etc, etc.
As noted, B5 worked fine. Legacies of War is a superb campaign (one of the best they've done) and the traveller mechanics support the B5 'feel' of combat (oh **** he's got a gun) far better than anything D20/D&D based ever did.
Equally, Judge Dredd works perfectly despite never leaving the planet, and...I'm honestly not sure if Strontium Dog has FTL comms or not.
The latter two don't really include any ship elements though, and B5's ship rules were just a bit random in terms of the effectiveness of different weapons. Prime Directive, one assumes, will include ship combat (we'll see).
To be honest, Traveller is a nicely flexible set of basic rules - skill checks, stats, etc. It wouldn't take long to home-brew some historical 'careers' and head off viking and set fire to some some dane or saxon settlements. In fact, an Uhtred Of Bebbanburg (Bernard Cornwell novel series), Ragnar Lodbrok (History Channel Vikings), or similar setting might be quite cool.
It's a genuinely awesome period of history that annoyingly few people seem to know much about* and has most of the classical fantasy tropes - multiple kingdoms at war with one another, small bands canonically tipping the results of battles (since the armies are big enough to be armies but small enough that a few dozen trained men really matter), duels between army leaders, politics and backstabbing, different nations within a few days travel of one another, religions (Christianity and Norse Paganism) at war as much as nations, itinerant merchants looking to make a living round the edges, pirate raiders, bezerker nutcases, mercenaries and traitors, etc, etc.
* Seriously, I swear most of the people I know seem to view British history as:
"The Romans" - "Nothing Happened" - "The Normans" despite over half a millenium of things, including most of the Vikings actually being the Vikings, the birth of a country and the only English king ever to qualify for a "The Great" badge falling in that gap.