I can't speak to risers, I've been afraid to use them and refuse to pay current prices for them. (I have a few 16x to 16x unpowered that do the job of separation just fine though)
this is a good point. 4 risers @ $25 a piece is the price of a new motherboard. people are throwing out 5 year old 'useless' core2duos that are no problems for mining. I was hoping that ASRock btc mining motherboard would ahve come with risers, but for 99 bucks you get the same motherboard as everyone else, just with a pile of 1x ports glued in.