The new wave of thrash is like the original wave: A few good gems hidden amongst a pile of shit.
That being said, Hexen, Merciless Death, Hatchet, SSS, and Violator are a few of those gems. I also like some Bonded by Blood, Municipal Waste, Toxic Holocaust, and even Evile once in a while.
Now, about this old-bands-releasing-new-shit-material thing. I think Megadeth, Anthrax and Testament are all still releasing good music. Am I going to sit here and say Th1rt3en and Worship Music are as good as Rust in Peace and Among the Living? No. Of course not. But I didn't think they were awful either.
Then again, if this new wave of thrash is as substantial as some make it out to be, perhaps it will persuade bands like Megadeth and Anthrax to go back to their balls-out thrash roots.