Mechanics-wise, I can already tell you what the big deal is going to be once people get their fill of i24 and i25 servers and want something more exotic: a server setup balanced completely around PvP.
PvP never worked out for CoH and the reason was simple: the game was designed around overpowered, superhero wish fulfillment -- and that worked out just fine for PvE, because mobs don't complain on game forums about overpowered heroes and villains kicking their butts.
And PvErs didn't have much of a problem with some power sets being more powerful than others for the same reason that comic book readers don't write angry letters complaining that Superman is more powerful than Green Arrow. City of Heroes -- and comic book inspired games in general -- exist in a special niche that gets away with imbalance in a way that no other game could, because that type of comic book universe directly translates into imbalance.
PvPers can't thrive in any of that, to be realistic. The needs of PvE in a super hero game pretty much mean that you'd have to overlay a completely alternate set of mechanics onto the PvP zones and enhancements, and when resources get tight, all of that is gonna start to break. Hats off to them for trying, but that plan was doomed from the start.
A server that's balanced around PvP from the ground up neatly solves those problems, with the one expense being that it breaks the super hero theme (any world with superpowers will be a noticeably imbalanced world, thus you have your Supermen and your Green Arrows). Which is not an expense I'd expect those PvPers to mourn over very much.
