Is it any good? His work has been hit and miss with me, with most of it being misses to be honest. Not that I hate it, just never saw why everyone says he's the greatest thing since sliced bread.
Did he write the "Code Red" or whatever arc? With the red cloud bomb that went off in Montana or whatever? It's worth checking out. Not as good as Busiek's stuff, but plenty entertaining.
I really liked him on flash, and some of his stuff on the titans is alright, but yeah.. I dont get the love he gets either.
I think he has some great stories. Some of his stuff is also kind of "Meh" though. What I find interesting is that all his mini-series are fantastic. JSA Power Trip, GL Rebirth, Infinate Crisis. Yes his regular series are "one good, one okay, one good, one ok" stories.
Despite not liking the concept, "GL Rebirth" rocked my freakin' socks off. I also thought the issue of Titans where Jason Todd fought Tim Drake was incrediblly bad-ass. I mainly asked 'cause I thought Johns was strictly DC and was surprised he'd done some work for Marvel.