I have the Line 6 Helix. I found one at Guitar Center, used (slightly, it's like brand new), and I saved $400 from the list. The reason I went with Guitar Center is that they are local and I have a 45 day return policy. I'm still concerned that I may not like the effects enough, or that the Helix may be noisy, or whatever.
So yesterday I spent about two hours messing around with the connections and getting to understand the user interface. Got my Boss volume pedal and Boss looper hooked into the chain, (no problem there,) and then tonight I spent almost 2 hours just stepping through the different sounds. Couple of things to say, and by no means is this an extensive review.
1) It's very well-built; solid, excellent feel on the foot pedals. Plus it's cool as can be; great LED lights, etc.
2) The UI is really well laid out, as all the other reviewers said. I picked up the important parts really quickly, and was able to build signal chains almost immediately.
3) There are 128 factory preset signal chains, (maybe 256, not sure). I haven't even stepped through those factory presets. Then there are another 600+ user presets; (I'm hedging because there are 8 "setlists", and there are 128 "destinations" to save presets in. So that's 1,024 presets. The first 2 setlists are factory, then there's 6 setlists for the user. Something like that, anyway.)
4) What blew me away tonight is the amp modeling. Frankly, up to now, I've had no amp model on my recordings, just the Cab Filter output from the Strymon Bigsky (a simple cabinet model that Strymon throws in on the BigSky). And then I have been going direct into the pc and I've not used amp or cab models in my DAW. But, wow! I recorded a loop of chord changes, added a delay (well, two delays) and a hall reverb, and just let it play, then I stepped through some of the amp combo models. Holy cow, what a difference! Really amazing sounds there. And lots of clean ones, too. I've never been much of an amp connoisseur, just using whatever, but stepping through not even half of the amp combos, I found at least 3 that I really love, and that make a BIG DIFFERENCE from what I've been using previously.
5) To continue number 4, most of the review I read said that you really need to buy the Ownhammer IR's (speaker cabinet impulse responses) and add them. Cost will be about $30. Reviewers just rave about the difference. So I haven't done that yet. I'm sure I will if I decide to keep the Helix.
6) Overall, it seems like the Helix was designed primarily for rockers, metal, cover bands, etc. Probably didn't spend a lot of time interviewing ambient guitarists for their needs. As I worked through the effects I was disappointed in the breadth of the effects that I could use. I'm not jumping ship yet, because I really, as I said, only spent a couple of hours on sounds, but I'm noticing a real emphasis on the hard rock sounds. For instance, I use a Strymon Sunset distortion pedal, and it's really clean, quiet and just adds a bit of grit or substance to the guitar sound. It has no noise at low levels and it's a beautiful "full" gritty sound. I haven't found anything like it's equivalent. I did find one distortion that may be usable, I need to play more with the parameters. And with the amp/cab modeling, maybe I'll find a slightly overdriven amp sound that I can use for some light dirt. Dunno, still hunting.
6) Delays and reverbs are the ambient guitarists main weapon. I did find some nice delays and the reverbs seem all right also. Again, didn't spend a lot of time but I'm not disappointed yet. There don't seem to be any "cloud", "bloom", "swell", types of delay/reverbs as I'm used to with the Strymon pedals. I'm thinking maybe the best thing would be to keep a very simple set of Strymon pedals, bring them in through the effects chain, and get the best of both worlds. I was hoping the Helix would be my "end all" rig, but maybe I need to be open to a hybrid approach. This is a big question that I will be wrestling with.
7) So far, the noise doesn't seem to be a problem. I haven't recorded anything yet, but I'm not hearing unacceptable noise from the Helix. Of course when I step through the distortions, many of them seem to scream noise, as do some of the amps. But I just don't use them, so no problem on that account yet.
8) If hours turn into days, and I still like the Helix, I'll download a couple of the free Ownhammer IR's, just to hear what folks are talking about.
9) As far as the effects chain, you can have up to 32 "blocks" or "things" in the chain, such as: guitar, compressor, distortion, effect loop, amp, effect loop, delay, delay2, reverb, reverb, EQ, noise gate, cab, etc. The effect loop can be placed anywhere in the chain, so the Boss looper for instance, can be placed before the delays, or very simply, move to after the delays. No wires to move. Pretty nice. Move the reverb in front of the delays takes about 2 seconds to accomplish. Once you have a chain you like, press the SAVE button, tell it the "setlist" and "destination", name it, and it saves it there. Sweet. Like I said, they really did a great job designing the UI.
10) Tomorrow I'll test more of the effect sounds, and hopefully make a simple recording.