We didn't encounter any noticeable interference when using the Rocketfish. But your mileage may vary: cordless phones, Wi-Fi access points, and even microwave ovens may cause problems (the same caveat applies to any and all products that use the unregulated 2.4GHz wireless spectrum). We also noted that when we powered off our Onkyo TX-SR805 AV receiver, the surround speakers made a "pop" sound for a fraction of a second. More annoying was the fact that we had to manually power on the transmitter and receiver units each time, even though we had plugged the transmitter into the Onkyo's switched AC outlet. Rocketfish should redesign the transmitter and receiver units to automatically turn themselves on whenever they receive power or signals. Furthermore, the Rocketfish electronics add an audible amount of signal delay, which made the surround sound more echoey than we would have liked. We were mostly aware of the delay on announcer voices when listening to the radio--it wasn't all that noticeable on movies.
Those gripes notwithstanding, surround-sound quality on movies was nearly indistinguishable from normal (wired) sound. We say "nearly" because the bass from our Dynaudio Contour 1.1 speakers sounded somewhat thin, and the treble had a harsh edge. But these shortfalls were slight, and we were listening attentively for differences. Less critical listeners--the same vast majority who can't tell the difference between MP3 and CD sound quality--will be quite satisfied with the Rocketfish Universal Wireless Rear Speaker Kit's performance.
Two final notes for HTIB owners considering this product. First, double-check that your system uses traditional bare wire ends for connecting surround speakers--newer HTIBs that utilize proprietary plugs (usually color-coded) won't fit the Rocketfish. Second, it's worth double-checking whether your system manufacturer makes its own wireless system. If it was purchased after 2006 or so, it's a fair bet that it does. Not only will the companion wireless kit offer guaranteed compatibility (even with those proprietary connectors), it may well cost less than the Rocketfish. For example, the Samsung HT-X70 would work fine with the Rocketfish--but you can get the similar Samsung SWA-3000 for a few bucks less.
The $100 Rocketfish can't compete with the best-in-class KEF Universal Wireless Kit--and given that the KEF costs six times as much, we wouldn't expect it to. Rather, the Rocket Fish Universal Wireless Rear Speaker Kit is worth consideration for casual listeners who want to cut those long speaker cords--so long as they don't mind a few relatively minor compromises.