I had a Helix since last October or whenever they came out. I was on the wait list for the AX8 and just got it a few weeks ago. The Helix is gone.
For the Helix I feel like this - when the initial videos were released it blew me away. I saw it at summer NAMM through Line 6 L2T speakers and the tones really let me down - but I wrote it off due to floor noise, beta release, etc...
Getting it home once ordered my NAMM feelings were only amplified. The interface was cool, but the sounds - I'll tell you this - I almost just returned it and kept my Boss GT-100. But, I wanted to give it some time so I kept it. It never got any better. Something about the sound of the amp models just rubbed me the wrong way. The only model I really liked was the JC120 if that tells you anything. I have never heard it in person sound anything like the videos - and that includes going to a Helix demonstration and training session at Guitar Center resented by Line 6.
Wanna know what it sounds like - look at normal channels on youtube. I like this one:
https://www.youtube.com/channel/UCpJrfCxQmio6zyjut4n0qRw
Yep, sounds pretty much just like that. Not bad, but not near the level of my AX8.
The AX8 is way more interesting and sounds amazing. The presets are ok, but the real good stuff is in making your own.