The Mathematical Model of the d20 System

[ValhallaGH]

I hope what you see of 4E matches what you know of 4E, for all of our sake.

If not, I'm heading to GURPS.

Don't do it, man. Don't hate yourself that much. I don't care how bad things get, doing that to yourself isn't the solution.

At least try the generic d20 variants before you dump that much work on yourself.
True 20 is a solid system that flows well and is designed for any genre. It even supports nigh-endless combats, while still being lethal; I ran a 56 round combat between two 7th level PCs and a hulking bruiser of a monster, and all three parties walked away at the end of it. On the other end of the spectrum, I've had a number of one to four round combats.
Mutants and Masterminds 2nd edition has the best d20 system math I've ever seen. It's a very slick system.
Grim Tales and d20 Modern work well for a variety of genres, though they both hearken back to a number of D&D flaws.
Spycraft, especially 2.0, does a wide variety of games extremely well. It's complicated sometimes but the math is pretty reliable (excepting boss encounters).

And then there's the less intense generic systems, such as Savage Worlds, Storyteller, or even the PDQ system.

Make sure you take a serious look at some of these options before you consign yourself to only using GURPS. It's a great system, fun to play, but NPC generation is a frakking nightmare.