I only recently got on the Valiant bandwagon, after having abandoned superhero comics for a long while.
So far, I've enjoyed:
Harbinger
Ninjak
Doctor Mirage (mini)
Divinity
Imperium
The Valiant (mini)
Ivar Timewalker
Overall, Valiant has a nice array of characters. The writing is rarely less than good and often much better than that. I rarely dislike the art.
I haven't read A&A or Q&W. X-O Manowar and Bloodshot don't do much for me. I've only read a few issues of Unity, which is OK.
One thing I'd say, as a complaint: Valiant doesn't have any truly compelling villains, except maybe Harada. But that's a minor quibble.
I pretty much avoid DC and Marvel these days, preferring Valiant, Image, Oni Press, Avatar and some Vertigo (which I guess is DC). Warren Ellis' Moon Knight arc was decent. IMO, Valiant is worth the investment...