I wont even comment on the benefits of bi-wiring, + or -. I have my biases and i have not done it it too long to feel confident.
But i will say that Millercarbon's comment is the most important one that we should all keep in mind, and almost no one ever asks.Many things work. The question is always "where can i get the most benefit for s given expenditure"
Right now i am placing most of my effort and money on sources (DAC, low jitter/noise sources, cartridge) and on room/setup. The sound, as it sits, is frankly amazing so I'm not out to change any fundamentals.
I believe most people can get the biggest changes from setup, room and source material (e.g.: the best recordings). Oh, and i make (or more accurately have and will) the costly electronics stuff i'm down-playing :-)
The great thing about bi-wiring is that with many speakers you can do a low-cost test -- even if the test is with lesser cables than the ones you own. This way you can separate two effects: a) wire sound (if any) and b) bi-wirign affect (if any).
G