Depending on the model, you'll find AirPlay, Internet Radio, video processing and even an automatic subwoofer phase control.
Pioneer's newest receivers all sport March shelf dates, but that's about all that the rest of the line has in common with the baseline VSX-522. If you're looking for a receiver on the cheap that boasts a front USB input, high resolution audio playback and Pioneer amplification, the VSX-522 will get you there for $249.
Stepping up gets you plenty more. The $379 VSX-822, $449 VSX-1022 and $599 VSX-1122 all boast DLNA certification, built-in Apple AirPlay, Internet Radio, and Control App for the iPad, iPhone and iPod Touch. The 822 offers 5.1 channels while the others jump to 7.1 and 7.2 respectively.
The 1122 takes things up another notch by introducing Pioneer's Advanced Video Adjust as well as 1080p/24 video conversion and Stream Smoother to clean up your streaming video and low bit rate files. It gives you automatic phase control as well, ensuring more accurate sound by delaying the sound from the subwoofer appropriately.