RUN:Best of DC: 71 issues 1979-86; DC Special Blue-Ribbon Digest 24 issues 1980-82; Adventure Comics 13 issues (#491-503) 1982-83. There were a few other digest titles as well, but these three are the only ones I know enough about to review (aside from pocket books like World of Krypton, which I consider a different entity).
KEY CREATORS: Too numerous to mention
OUTLINE: Reprints of various DC comics (both DCU and not) with the occasional new story thrown in on rare occasions
STANDOUT ISSUES: Best of DC: #35/etc Year's Best; DC Special: Doom Patrol issue; Adventure: #500 numerous Legion reprints. Numerous great stories appear throughout
DUD ISSUES: None stand out in my mind. You can probably find some weak stories throughout
OVERALL: Most issues had a surprisingly decent percentage of good story content. The best of all the digests were the Year's Best stories, which gave a great sampling at DC titles at their best. I think if Best of DC was revived as an Annual with just this feature, it would be a good way to hook readers on titles, by presenting the best it has to offer. Though not DC Universe, the Sugar & Spike stories were always fun. Since Best of DC and DC Special were organized by theme, one could readily skip issues that didn't interest them. Perhaps this is why Adventure, a non-themed book was my least favorite. Beyond the Legion reprint I wasn't impressed by most of the stories, except for a solid new Shazam! story in the first few issues. People who are not fans of the Silver Age should be aware that most digests (except year's Best) contain a healthy dose of Silver Age material. This didn't bother me as a kid but probably would now that I have a better ear for dialogue. Also given the size of the books, you may have to squint at the lettering somewhat.
RECOMMENDED OR NOT: All are recommended to some degree or another, though Adventure least of all. For DC Special and Best of DC, unless you're really in a sampling mood I'd skip the themes that don't interest you.
CONTINUITY NOTES: Probably most stories only exist in some Hypertime world or other now or have been really altered. The Xeen Arrow story was implied in the Green Arrow digest that reprinted it to be a tall tale by Ollie