In short, the Armageddon one-shots are a pseudo-universe reboot given the problems the official Wildstorm reboot suffered through. Each issue focuses on one character from each of the main teams (Stormwatch PHD, The Authority, Wetworks, Welcome to Tranquility, Gen13, WildCATs) and takes them into a post-apoc future where Void (who serves as time-travel enabler and deus ex machina) encourages them to find out what happened and work to stop it.
This mini-series was written by Christos Gage (who already outclassed all the other big names involved in the Wildstorm relaunch) and he does a pretty good job of delivering six one-shots around the same key issue. Not every issue is gold - Gen13's "find your family" message is pretty pointless compared to the Authority's "save all of London" - but the overall standard is pretty good.
***SPOILERS OF SORTS***
Okay, the world-destroying event is suddenly a huge number of superpowered beings suddenly starting large-scale fights all over the world, with the resulting fallout being lots of property destruction and the near extinction of all normal humans. It's interesting to see how several different characters react to this and Gage writes them well - Wetwork's Dane is so myopic about fighting the Night Tribes he misses the bigger picture (although Void's deus ex machina doesn't correct him) while the Midnighter's inital concerns are blunted by the rest of the Authority's blase "Oh, an alternate post-apoc future? We'll fix that when we get there". As an introductory issue for each team, it works very well.
However ***DEFINITELY SPOILERS HERE*** it's pretty obvious what the big twist will be. Armageddon: Stormwatch PHD #1 showed a much older Jackson King behaving very much as a dictator. Although driven by the probably respectable goal of "find who's responsible and kill them", he's pretty short-sighted about it. The Stormwatch space station gets good readings of Void's temporal signature, so it's pretty obvious that King will try to use Void (shown in bondage elsewhere) to come back in time to 'save' the past, only to doom the world to the exact fate he's trying to avoid. Alternatively, it could be the sekret big bad that Gage has hinted exists in some other issues, but I don't think he'd waste the big bad guy on something he can pin on an existing character like King.
As someone who has come pretty close to dropping Wildstorm entirely, the Armageddon series has at least made me want to keep collecting them for a little while longer (but it's currently only two core titles, so it's hardly a big effort). The Authority Prime (also by Gage) has thus far been a long fight between Stormwatch Prime and the Authority, but it's been an entertaining one.
Of course, the DC vs Wildstorm Dreamwar series is coming up, which may see me abandoning things in disgust as Batman beats up the Midnighter and the DC heroes give the Wildstorm heroes a stern lecture about their behaviour.