Lior KK6BWA is in the process of hacking the Baofeng UV-B5. He writes:
As soon as I got the radio, I took it apart. I did not even use it, just turned it on to make sure its not defective. It looks like Baofeng has redesigned this radio, but they are still using the RDA1846 chip for the 2M/70cm radio and the RDA5802 for the FM radio. Additionally, they have added more circuit isolations between circuit blocks, which should makes this radio a better receiver.
And the best part… They have separated the CPU board from the radio with a flat 30 pin FPC cable (0.5mm pitch). This should make this radio very simple to hack, since we could design a separate board and place it on the radio.
If you want to read more and follow his progress, go here.