Okay, I've gotten a look at the second "Tom and Jerry" DVD collection, and I have good news and bad news.
Good news: The original voice of Mammy Two-Shoes appears to be intact in most of the cartoons. And the blackface gags in "Mouse in Manhattan" and "Safety Second," often cut on TV, are intact here.
Bad news: There are three cartoons where Mammy's voice appears to be in a different acoustic from the rest of the cartoon, and she sounds like a voice actor imitating the original. These are "The Lonesome Mouse" on disc 1, and "Saturday Evening Puss" and "Nit-Witty Kitty," both on disc 2. Apparently these "redubbed" prints are from a British Tom and Jerry DVD -- Tom and Jerry are huge in England -- where Mammy's voice was redubbed to give her a marginally less exaggerated accent.
So what have we got? We've got a set where WB has not chickened out, and has included the original Mammy Two-Shoes and the blackface gags. But we've also got a set where three incorrect versions appear to have been included, not out of cowardice, but out of poor quality control. (I'm assuming nobody in the production process noticed that the voice in those cartoons wasn't the original; that's the only explanation I have for why Mammy would be redubbed there but not anywhere else on the set.) Warner Brothers gets a lot of good press for its DVDs, and much of it is deserved -- but they have some unnerving and frustrating quality control errors sometimes. This appears to be one of them.
As to whether the set is buying in this form: your call. I would say yes, if you like Tom and Jerry, because of the chance to see those other cartoons uncut. But mistakes like this just shouldn't be made on a major release.
Also: I'll bet you anything that WB gets more complaints over those three re-dubbed cartoons than they do over Mammy's real voice in all the other cartoons.