I'll chime in here:
I routinely use my X32 with X3e. It's a solid combination. As mentioned above, I yearn to have 'bus switching' capability with the Mackie Control Emulation functions. I've submitted a feature request to Behringer for this function. They shouldn't have to work hard to make this happen, as it's a part of their BCF2000 product function.
Other than that, the main attraction of the X32 (for me) is the ability to deliver great headphone mixes with effects to the performers. The high quality compression and reverbs of the X32 help to build excitement and confidence within the performers, while I leave X3e at a relatively high (and untouched) latency setting appropriate for mixing, that is fully de-coupled from the monitoring functions. The other convenience is that the flexible routing allows me to use my Focusrite, Golden Age, and ART preamps into the 'Aux-In' ports of the X32.
I also run two sets of 2.1 speakers from the X32 for mixing and review, and all is well. As you can tell, I'm a happy camper, but I'd be a bit happier if there was away to have motorized faders on my busses in X3e.