I regularly use the FlexRadio for CW. With the proper settings, the latency while sending is minimal. I have no problem using the built in software keyer at 25wpm or so. However, please keep in mind that there are several things that can greatly affect this. First, a high quality sound card with ASIO drivers is a must. I use the Delta 44 sound card. Also, there are several settings in the PowerSDR program that can affect latency, such as Sound buffer size and DSP buffer size. These settings have to be balanced between performance vs latency for good cw operation.
The T/R switching however is slow, and is not QSK. The SDR-1000 uses a loud and slow relay to switch with, and in my opinion this is the SDR-1000's biggest weakness. In my opinion, if the SDR-1000 used diode switching instead of a relay, something close to QSK would be possible. Right now however semi-break in is only avaiable and for quick CW exchanges I manually key the T/R switch in the PowerSDR console.
Despite all of this, I still like the Flex radio on CW because if its receiver, it is the best CW receiver I have heard, and that includes my K2.
73,
John KD8K