I actually grabbed the demo version of the sim and tried it with my UA Apollo, but, while the tones were very pleasing, and I *really* wanted to like it as something to use for a company setup, there was this latency I couldn't seem to get rid of. Not sure if it was completely in my head, but I wasn't looking for it, and it's something I noticed, so it's probably not all imaginary.
Contrast that with the Boss Wireless setup I got very recently, where I *was* expecting some latency, but do not actually notice anything at all.
If you want to get your JCM saturated, try layering it with an overdrive pedal, nothing extreme, as that can get a bit squirrely.