I believe that mine are the original CD's - they have the "AAD" stamp on them, which I believe means they were simply copied from the original albums. In any case, they don't sound that great.
They did release that four-CD box set in (I think it was) late-1990 (my buddy had it) but I got all the individual CD's instead.There were too many good songs missing from that package.
But they were chosen tracks, not all the albums. I think it's a great thing that we can get all their albums with XXI century quality!
Also, Matt, yes, you're right. Those late 80s vinyl > CD conversions were admittedly rushed, using plate-oriented equalization settings - hence the not-so-good sound quality.
I believe the songs in Mothership were remastered too, but most of them used the remaster from the Boxed Sets anyway, so... YES, the whole album package in remastered quality is something to keep an eye for! They will sell like hot cackes.
waiting for the snow a lazy mind has just thrown myself an unsolvable 1 million$ question
is Bonzo the best in following and covering solos or is Moonie?
"posterity will judge" ..
) 
So I guess Moon wins there.