Finally FlipKey proved me wrong and proved itself right, if you see my previous post about them here.
I had kind of hinted that there seemed to be a 'club' behind it, but it doesn't seem to be true after all, apologies. They let me into their wondrous website and the whole system looks to me, after a month experience, quite innovative and well meant.
Its main flaw is that since it's ourselves inviting the clients to leave a review the clever among us (notably not me, as you can tell from the percentage of not so good reviews) may be tempted to invite only clients they know were satisfied. So for those inviting all clients the chances that the unhappy take proactive action is, attending our own rather long standing experience, 5 to 1 compared to those clients that upon check out had reviewed the apartment and the whole experience highly in the review-form they hand to the agent.
Anyway I do think this is a great service to our industry and that on the long term flipkey may become a must for the savvy traveler.