I'm using an HXFX. It works really well using a 4 cable method allowing FX in front of the Kemper and also after the amp stack. It sounds great, is very easy to call up and edit FX and has comprehensive switching facilities for control of the Kemper. I'm using it in mono as the Kemper is perfectly capable of running stereo in the post stack FX section if required.
I haven't run into any cons as yet.