This is exactly what has ticked me off with GURPS - the sheer amount of chargen options and the complexion of character generation. I've also thumbed once through GURPS: Vehicles and it looks complex, probably even more complex than Striker, and I've heard that WorldGen is also very detail-oriented. I have nothing against this in general, but it doesn't fit my current style too well (though a part of me loves gearheading, unfortunately I have very little time to gearhead).
But how many books do you need to play GT well? GURPS mainbook, GT book, Ultratech, Vehicles and First In, or could you play the whole range of Traveller in it with just the mainbook and the GT book?
Well, it depends. If you want to use all the traveller material you'd need gurps 3e, the compendiums and all the traveller stuff, mainly the main book, the alien races modules and the starship system, plus ground forces. You don't really need vehicles for the traveller ship design, the main book and GT starships would do.
The main traveller book doesn't have the stats for some races so the alien races modules would be needed for the whole traveller experience.
If you want to run the ISW period you'd need 4e, the GTIW book and ultratech 4e since the dolts running the gurps end of SJG left weapons and gear out of GTIW. The ship combat system is nicer in GTIW but not totally compatible with GT's rules so you could not use all the advanced rules and goodies in GT starships.
LKW did say that there is a plan to someday update all GT stuff to 4e, but when that may happen and what format it will be in are still unknown.