It is cheap and it works. It's reported to have better range than turnigy 9x stock receiver.
There are two types. The 801 has no amplifier and is limited to 300-600m (I'd stick to <300). The 802 has amplifier and filters and can theoretically reach the same distance as the stock frsky receivers. midelic on rcgroups is the guy who made the firmware for these, there have been several updates since, adding SBUS, telemetry etc.
At the price of the F802, you might want to just buy an original FrSky V8R7 or something.
Depends on the CC2500 module. Most of the small ones are extremely limited in range (the "blob" types with pcb antenna even seem to have a range of <50m in some cases). And the amplified ones usually cost as much as the 801.
SBUS? With the recent firmwares by midelic, yes. On the 801, you need to do some soldering, though (wire to a pin on the atmega 328p).