I went with RadioPopper due in part to the interference problem (and a few other reasons). Great product, but the company's not so hot... they're months and months behind on product release dates (ie I was told their new JrX would be out "on time" in April, May latest, a week before they were set to ship... they still aren't out. You can't tell me they didn't have some sort of idea a week before that they weren't gonna make their own deadline) and their website is never updated. They're also a bit pricey (you can't order a transceiver, it either sends or receives, not both like some of the PW's can)... but like I said, great product. The only thing they don't have that I kinda miss sometimes is a second curtain sync option (which the PW Multimax can fake by delaying the flash output signal just a pinch) but Canon's Wireless E-TTL doesn't have that anyways so it's not like I lost anything.
You could always whip out the pc cords too