The UI is really good.
The modelling across the other products, Helix, Axe Fx, Kemper are all very good now and I think that is just personal preference, but excessive menu scrolling does my head in.
The Helix screen shows you the signal path. You just use a joystick / button thing to pick a space, click it and then insert the fx / amp / cab / ir / whatever into that spot.
Then there are 6 knobs on the bottom that become the controls for that individual item, so controls can be adjusted the old fashioned way.
The footpedals are even touch sensitive so you can just touch them to show the controls for that individual item without actually turning that item on / off. Each footswitch can be assigned to do 8 things at once - from changing a drive parameter on an amp, to simply turning some things on while turning others off, or use as a momentary to speed up a rotary cab.
The expression pedal can be used for wah or volume or to change any other parameter - or more than 1 at once. So you could increase fuzz at the same time as increasing reverb mix.
Some users have added the Source Audio Reflex midi expression controller to be able to do extra things - like running 2 wah's at once, but in opposite directions (I don't know why either), or controlling LFO.
It also has 4 loops so external pedals can be used and placed anywhere in the signal chain. The loops can either be used as simple Send and Return in the same place, or can be used to send, miss a block, then return so bypass other things at the same time.
The outputs can be configured so, for example, the XLR have cab sims, but the 1/4 inch doesn't.
It's just a hugely fun bit of kit that is dead easy to use. And it now has a decent PC / Mac editor too.