Plex is a win for nobody except the guy with the highest limit on his VISA and the RMT'ers.
Look at the other game and how the DRF came into all those Supers.... Plex for isk. Bought supers from NC. NC RMT'd all the iskies.... It all started through the Plex system.
RMT bot accounts in Eve-- It is cheaper for them to Plex those accounts then it is for them to actually pay for them. Plex maximizes RMT profit plus you can't track 10000 accounts subbed via Plex like you can if they subbed with a credit card.
CCP tried to use Plex to curb buying ISK not to make it easier for people to maintain subs. Plex was a piss poor reaction to the RMT problem Eve already had. The decision to add Plex to that game came and bit them in the arse when the RMT'ers used it against them.
CCP rolled out the MT store as a way to create a Plex sink because of the massive stockpiles that were sitting in hangers as well as sucker some folks into buying $1000 jeans. CCP saw a ton of profit from Plex however all those Plex were sitting in hangers while they had spent all the profits designing 2 other games. CCP claimed those Plex as profits when the original GTC were sold. How many $$$$$$ were just sitting in hangers while CCP didn't see more profit yet still had the costs associated with the game?
Plex may seem like a good thing initially but there are way too many pitfalls associated with it down the line.
For ease of argument just go to the old eve forums and search the old Plex threads(better yet use Chribba's eve files instead it is better...).. Every argument is there.For and against.