You're right about the XLR out, and I could use that a handful of different ways to get sound externally from the amp. I just really don't like being restricted to the built in IR's when using the XLR though - and I think you can only use one even if you have multiple ext cabs. Would be nice to get multiple ones for a mix.
Hopefully they make it so you can put your own IR's in there at some point. Also, I have a 15w IRig amp from IK, and its Class D with a cabinet out and it works fine. Most ext. cabs are 4-8-16ohm. This standard is very easily implemented in a class D amp, and is done quite regularly with amps for automotive, radio, instruments, and more.
Yeah, to my ear its a bit bright (actually the highs can be brash on some of the models)...but the speakers are also brand new and yet to be broken in a bit. Its all good. For the money, this is actually a really good little amp, and I'm glad I've got one. I will be nice to just take a guitar, cable, and an amp to jam with some friends. When they expand the FX capacity it will be even better.