The End (or, What Should Have Been "The End")
Despite the frustration one undoubtedly has from the resolution-less Rise of the Third Army storyline, and the sheer insufficiency of the First Lantern as a palpable presence as a universe-threatening villain, the overall effect of this collection is one of enjoyment, tempered as it may be if you have read a number of these issues in the individual series collections. The First Lantern is as unmotivated a villain as you'll ever read. Apparently his big skill is showing potential variations of life paths while siphoning emotion (making for rather dull intermediary episodes in the pacing of this event), but he can't do that and keep track of where women are or the actions of entire planets at the same time. But he's a menace, apparently, nonetheless. Coupled with this, the biggest disappointment story-wise is the destruction of Thanagar for no meaningful reason or purpose. It's one of those "let's kill off a major character 'cause it's the end of the season and we don't have any fresh ideas" sorts of moves that should not have happened and shortchanged the characters and audience far more than any potential good it could have done. Still, unless you really care about Sinestro, it might not bother you too much.
The obvious highlight of the storyline/collection is the massive Green Lantern 20 (assuming that's the issue, since this collection like so many doesn't want you to know what issue or what series you are currently reading). As far as slam-bang finishes go, this even surpasses Grant Morrison's finale on Action Comics. It may not get any more slam-bangier than this, that's for sure. Everyone (well, not the early GL Corps supporting crew, who have mysteriously all disappeared) makes an appearance, even characters that don't have much to do with anything, giving us Mighty Mighty Battle Scenes and Splashes of Wow all over. Sure, this doesn't give us much time to digest or feel any emotional impact from any of these major twists and pops and booms, but it does do a fine job simulating what it might be like to ride a roller coaster without any of the devices that ensure the cars stay on the tracks. Certainly the real highlight is the optimistic, heartwarming epilogue, with everyone having a happy ending. It almost makes you wish it was the last issue entirely, for it is such a great way to end it all. Of course, the series continue, and while some of them give us their own epilogues, none of them have the richness of GL 20 (unless you are a big Kyle Rainer fan). The Red Lantern stuff is still weird and forced and obvious and a bizarre combination of visceral appetite appeal and Lovecraftian weirdness (though not to his level, natch), but you don' have to think about it too much. It all reads quickly.
With all the general positive resolutions (except for Sinestro, of course), this may be the best standalone GL collection of the bunch. The basic wonderfulness of the ending and epilogues will likely override any of the irritations of it, especially if you don't read any issues after this collection.