BTCguild with their 1 hour delay on stats makes the simplest PP system practically hopper proof.
I doubt that, hoppers are just too lazy to hop it properly.
It's true. You can still hop it in exactly the same manner as before, it just is less effective. To make proportional hopper proof you need a delay that is longer than a round could ever conceivably be.
Well, one could delay the stats by 3 hours which on BTCguild would cover the majority of rounds(at this difficulty)
but since there are very many rounds in the area of an hour it basically keeps most hoppers away.
Maybe if/when there are no more other good PP pools the hoppers would work harder and try to hop there as well.
bitHopper allows hopping using LP. It has been successful for me. Almost on par with normal prop pools, and better than using btcguild with the delay.