the biggest incentive (I see) for using CEX.io/Ghash.io is one major thing, a lot of pool owners have said no to...

auto-payouts with splits by percentage

Which makes it tons easier when I have a friend that wants to throw some money down on a miner and have me toss in the rest + host it, then I just have to put in an address and what % he gets, what % I get... and nothing else. No more screwing around with spreadsheets, no more bullshit.

Awhile back I asked several 'group buy leaders' in PM how they did the split %'s on shares in miners, the answer I always got back was 'spreadsheet'. Seriously, a spreadsheet... I was debating on making something to handle the splitting for myself in PHP or some other language, however CEX.io/Ghash.io came along, 0% pool fee, splits everything easily, bam, sold.

Not to mention when people ask me why I use it, I tell them that and... then they start using it for the same reason. Obviously a feature a lot of people overlooked, plus merged mining in IXC, DVC, NMC is also a damn good perk.

EDIT: Yes, I did copy/paste this from my post in the other thread. I would like to add in the fact, Ghash.io continually is updating their interface and services, something not seen much from pool owners these days, not of this speed anyway.