I owned the Axe FX II, which I sold due to the complex front panel user interface ( I don't want to go via a PC editor ) and bought the Kemper Rack, just before the Helix was available.. The Kemper wasn't quite what I was looking for, notably because of a lack of parallel routing, and certain other options.
I was hesitant to buy the Helix, as I'd previously owned the Line 6 Pod Pro HD X, and was not pleased with it, due to the quality of the amp/cab sims, although I thought the effects themselves were excellent.. You can read my review of the POD Pro X, Kemper, and Boss GT-001, on the Thomann site..
After having looked at some reviews, the manual, & listening to some sounds on Internet, I decided to sell the Kemper & go for the Helix.. After all, you can return a product to Thomann, if not happy..
Well, there was nothing to worry about, it's very very good.. It's solidly made, the user interface, and beautiful colour screen, are easy to understand, there's parallel routing, Mic input with phantom power, the possibility to install IR's, plenty of connection possibilities, including the Helix control pedalboard, and it sounds fantastic..
This is just what I've been looking for, and I would have gone for it straight away, in preference to the Axe FX II & Kemper, if it had been available at the time.
I have no intention of changing this, I can't really find anything to criticise.. It does eveything that I want, and it does it well..
I should mention, that this & the others I have mentioned, have been evaluated from studio use, not from live work..
In summary, a really great product. I can definitely recommend it, if you're looking for a high quality, versatile
preamp / effects unit for studio use.