Here's the best source for direct comparisons between the UE transfers and the older SE DVDs which used the same master sources that MGM used on all their 90's era video releases. (FF, this is why that same stubborn hair in the gate under the Rack is in Thunderball from 1989 to 2002. Same recycled transfer but better pressings over time.)
http://www.bulletsnbabesdvd.com/forums/viewtopic.php?t=3053
You can also see screencaps form the original Region 2 editions which were released first and had issues that were corrected for the Region 1 discs. (Though hastily.)
Overall, I think that they nailed two or three of the films imagewise-those being Dimaonds are Forever, The Man With The Golden Gun, Moonraker and Licence to Kill. DAF is quite close and looks stunning though some of the colors aren't quite 1971 vintage. TMWTGG is stellar though I don't see enough Technicolor. Moonraker is one of the best transfers I've ever seen and the colors are about 99% accurate. LTK is very very slightly different, but fantastic and is the only release that is fully uncut. (save for some rumored obscure foreign releases back in the early 90's)
Other verdicts: (those with * look better on old editions)
*Doctor No, *FRWL, *Goldfinger: had some amazing cleanup work done, but the color seems to be off and downright muted in most places.
*Thunderball: Clean but with wrong color all over the place. Needs a re-do.
*YOLT: Lacking color that showed off the sunny countryside of Japan. Missing all the deep yellow/brown/orange tint of the 1967 presentation. Re-do.
*OHMSS: Framing a bit shifted to the right, a very tiny shot was accidentally inserted in error, opening blue tinted, some audio errors, no 60's Technicolor look. Re-do.
LALD: The UE DVD was shorn of grain structure and very soft. Contrast boosted and not good looking at all. This has been corrected for the most part.
*TSWLM: All transfers don't look so hot. The film was shto with a lot of soft focus and diffusion which has never been replicated well. The UE removed the original color timing and was full of edge enhancement. Original audio was missing as well. Re-do.
FYEO: Great detail in the UE but some definite color manipulation. Overall great, but slightly different from original.
OP: Same here, great improvement in detail but slight color manipulation.
AVTAK: Looks fantastic, and like a print of the film almost. Color spot on if a bit tweaked. However, the opening teaser is horribly cropped, and you lose information to cropping on top, bottom and sides of the frame throughout. Without the cropping this would be close with MR's transfer.
TLD: Great transfer, very slight modifications to contrast and darkness levels but only to improve the image for home viewing. Great job.
GE: Different color timing which may or may not be Theatrical. Looks better on the whole. Has the cropping issue which has never been confirmed as an error. Audio is a remix from stems and lacks the huge bassy punch of the original.
Tomorrow Never Dies: gets some major improvement and actually looks like the theatrical presentation instead of video. Audio is a remix and quite good, but nowhere near the incredible theatrical mix. (One of the 5 or so best surround mixes I've heard.)
TWINE: Looks better overall, some contrast boosting, less grain, color may have been tweaked a little. Audio likely a remix as well and lacks the matrixed original 6.1 track. Framed to give a bit more on the top edge.
DAD: UE is better but lacks the original soundmix design of a matrixed 6.1 track.
These are my quick opinions and nitpicks for the most part. As I said 99.99% of people are going to be thrilled with the new set. And as a bonus all the new transfers have the original theatrical subtitles/location text and correct aspect ratios.
Another image comparison, though primarily of European editions which have the wrong colors on some UEs: