I've always been a fan of lengthy, descriptive skills lists, and subskills, even if the players won't ever use all of those skills...I use them for NPC's.
When ICE's Spacemaster came out, it was a godsend to me.
Looking at something like Unisystem, and subset of it Armageddon, Con X 2.0, Buffy the Vampire Slayer, I can't stand a chearacter that has all sorts of generic skills, "Get medieval" for all hand to hand, or "Gun Fu" for all combat, for example.
With a system that has narrowly defined skills, I always provide NPCs for the story, to accomplish those things, with the PC in leadership positions.
I hope Mongoose does a good job. If not, I will always have my older editions, because in the end, it's more the story than the specific system, I think, unless the system itself does not lend credence to the specific background / setting.
Someone else here said it. "Base mechanics on play, and play on mechanics."
D6 SW was better for me than using Traveller to do Star Wars. And is still better than d20 Star Wars.
Classic and T4 work better for me, than 2300 did.
Obviously system itself is a very diverse discussion, because one guy's GURPS fondness for detail is another person's headache.
And I know people that still play and love Tunnels & Trolls.
Plusses for Mongoose: They certainly know how to do slick work. But something generic, to fit all Sci fi, I think has been done, with GURPS, D6, Alternity, and d20 Modern/Future.
And as far as that goes, from where i sit, GURPS traveller revitalized, and gave new energy to Traveller, as did T20, (though I don't play it).
Will this new enthusiasm for Traveller among the non-grogs convert over to Mongoose, riding the wave to shore?
My prediction is that it'll sell, but in the end, won't feel like "Traveller" to the old school as much as CT / MT. Reinventing itself, the way GURPS:Traveller more or less seemed to will be a good thing, for the new generation, but in the end, I think that the more dedicated CT grognards will seek out the grail from the font himself, Marc's T5, or keep playing CT, as they have everything for it, already.
Just some thoughts.