Objectively speaking, if you have and like the One, you should have no problem with the Max, because for the most part, it's the same device. Same form factor, same processor, same UI. I think most of the lackluster reviews have more to go with it not being anything mind-blowing, not necessarily that it's a bad device.
The main differences are as follows:
- Max is much larger
- Max is plastic wrapped in aluminum (similar to One Mini) vs the One's all-aluminum chassis
- Max has expandable storage
- One has OIS, Max does not
- Max has fingerprint reader
- Max comes with updated Sense 5.5 (coming soon to One)
- Max lacks Beats audio
So you're gonna get pretty much the same user experience, but with a few differences. So if you want a One, but jumbo-sized, I say go for it.
Incidentally, in my case, I kept looking at the One, thinking: "if only this thing had a microsd slot and bigger screen". Then *poof* the One Max is leaked.