I recently had the privilege of reading the Douay-Rhiems Bible with Challoner's own notes(1). I can now verify the following: this is a truly lousy translation. Because of its reliance on the Vulgate, it has some pretty doggy translations - angel where messenger was meant in the original, humility for low estate in the Magnificat, etc. Challoner's notes only make it worse: they claim complete knowledge of the background to the work, so that the good bishop is able to explain away (unconvincingly) points such as Jesus answering Mary back, Joseph the father of Jesus having two different family trees, etc. It also contains notes stating tha all Protestants are going to hell, and some rabidly anti-semitic exegesis. Amazingly, the copy I had had an authorisation date of 1950.

More stupid footnotes in the DRB:

'Even though the Bible says he did, Jesus had no brothers or sisters. The Holy Bible is, er, lying.'
'See how Judith slips into veniality in deceivingHolofernes...in order to righteously cut off his head.'
Speaking of Judith, the DRB attempts to place this totally fictional story in an historical context.

(1) Not his own handwritten notes, but a copy with his own annotations transcribed and printed. You know what I mean.