As much as I hate to admit it, in the end the reason I moved away from the Helix was that I just wasn't getting what I wanted from the deleays and reverbs anymore.
Transistor Tape, Cosmos Echo, Adriatic Delay, Bucket Brigade, Elephant Man, Glitch Delay... those are all REALLY REALLY GOOD.
But the bog standard Digital 'Simple' Delay... it's either too simple, and not doing what a DD3 or DD8 would do behind the scenes... or there's a bug that was never caught. It doesn't 'pop' in the mix, it doesn't give you enough echoes at medium feedback settings, it's like there's the whole lost world of tweakery between 80-85% that you can't access. Hard to explain, but very difficult to balance.
I could never get the digital delay I truly wanted from the Helix, after trying for years and years. I just sorta accepted it as fact. But then whenever I'd go back to a DD Boss delay, or the LVX, or anything in Fractal land ... it was truly a different experience. It could be due to companding, it could be due to some sweetening going on in the circuit, it could be to do with some interpolation method that affects delay quality. I don't know. But this was a strong motivator for me to move on.
And then reverbs ... man.... I just never liked them really. Even when they added the Dynamic ones and Fannymede and all that jazz.
I'd really like some reverbs that can hold a candle to the UA Golden, Meris MercuryX, MXR Reverb, Fractal etc. Even my Boss RV-5 has a nicer modulate reverb mode and Hall mode than the Helix.