Personally, I used to oppose the idea of Open Only for Powerplay, but now I'm simply neutral to it. The reason why I opposed it was that I was convinced that Open was pretty much dead (I rarely ever saw anyone in Open, even at CGs or other "hot spots"), and felt that OOPP would be the nail in the coffin for a system that enriched my game, even though I'm primarily a BGS player, and that I really wanted to be improved.
What changed my mind was Sandro's statement that the majority of players played in Open, by a "significant margin." This was so contrary to my experience in Open that I was convinced that Sandro's statement was a "statistical truth." Then I
ran the numbers, and started keeping track of the few players I'd encounter at CGs, and "hot spots," as well as doing BGS work in Hudson's capital and what should've been a busy control system, both during my local prime time when I was home sick from work during the weekend,
and during my normal play window.
So far, the results have been fairly consistent with the idea that the game's matchmaker considers the
quality of a person's connection with whoever is hosting an instance first. IOW, you're much more likely to instanced with someone
physically close to you, than you are someone half a world away. If you don't play during your local prime time, the effects are similar to playing in solo, even if you play during
global peak players.
So while I think OOPP won't have a huge impact on the size of the Power Playerbase like I'd feared, I also think it won't generate the
fun kind of PvP that many OOPP advocates believe it will, nor will it allow them to control 5C activities or botting via PvP. In the case of the latter, 5C players and botters can simply raise their router or firewall's security settings*, and enjoy the benefits of solo in Open. It may stop the lazy or stupid ones, but most will adapt.
As for the former, in my experience the type of player who hasn't
already pledged to a power because PP isn't OO, isn't the kind of player who's fun to play with in the first place. They'll pledge, discover that that there aren't any "easy kills" like they hoped, get bored, and quit. Meanwhile, those of us who are interested in actually helping our Power, as opposed to PvPing for the fun of it, will avoid PvP like the plague, because PvP in Powerplay is all risk, for no reward. If we're carrying merits on board, it makes far more sense to disengage and turn them in than to turn and fight, even if we're equipped for combat. And, of course, the type of player who wasn't
already playing in Open, but didn't quit due to OOPP, is far more likely to combat log than most.
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* We have a tween at home who is far too computer savvy for her own good, so as a result our internet security is very tight. Every time there's an update, I have to re-enable Elite's permissions, because our Firewall treats E: D's ports as high risk.