If you are using remote head with the 996XT, it will not work with the 996P2.
The serial driver for the 996P2 is a little different, since it's using USB. I use a program to control my BCT15X, 996XTS, and now 996P2s. However, when the 996P2 is off, the serial port goes away in the computer's eyes, and the software, which is a expecting the serial port to be there hiccups. Yes, the program could do things differently, but it isn't an issue with the older scanners.
I don't think the 996P2 is as good as a receiver(including simulcast p25) as the BCD536HP/BCD436HP. However, I think it's a good value for the prices available currently. If you were using the remote head or serial to control, I don't think you'd notice any difference in using the 996P2 via the keypad, and you'll be able to hear Phase 2(although a little muffled).