Pro's
SE is paying for bandwidth, Got less if you're not logged in.
SE is paying for Server repairs as they burn out parts because of use, everything has a mean time to failure. Less load last longer Cost less over time.
SE has more money to do upgrades.
Server have little to no login queues. (with WOW, I recall weight 40 mins in a queue to log in, now that's a waste of my time.)
Less server leg.
Con's
Pay may need to re log in.
You can't step away form your computer well waiting in a queue for duty finder. (well point of duty finder was so you could do other things well waiting for party to forum. go Craft / fate farming / gathering.
World seem less full(but not really because there are so many people playing right now.)
Inturn Pro's out way Con's
And if this is go game breaking go find another MMO without a AFK timer, FFXI is bleeding players and you could use you, and it's AFK kick timer can be turned off.