I love my INSTRUMENT 1 to death and use it wherever possible, but I also have a K-Board Pro 4 and a Linnstrument 128 (which I haven’t even unboxed yet; my first one went to a friend in Finland and I just replaced it) and the difference in MPE implementation is pretty drastic. As the guy who reviewed it for a major magazine, and who’s been playing one for over a year, I think I can speak with a reasonable amount of knowledge, if not entirely without bias.
The INSTRUMENT 1 is inexpensive but NOT cheap. It’s well-built, light, and works well mechanically. I find it easy to play and configure, and yes, it requires some finger toughness (but nowhere near what a guitar or bass requires). The iOS and Mac/Win control apps are very well written, clear, and easy to use. Overall it gives the impression of something designed and built with care.
That said, Artiphon has been struggling with disgruntled users for a while now. They’re way, WAY overdue for a firmware upgrade, and the I1 is missing some fairly fundamental features that are vital for good MPE use, most specifically and importantly, pitch rounding (which it doesn’t do at all – you either play fretless and hope you have good aim, or play fretted and give up sliding to bend).
I have some other gripes but they’re personal (I believe, as apparently few others do, that there’s still a place for global gestural controls like pitch bend and modulation controls on MPE devices).
Considering that the INSTRUMENT 1 was designed and shipped before MPE even existed, I think the makers can be cut some slack… but yeah, they have got to get pitch rounding working ASAP or they’re going to get left behind. All that said, I end as I began: I love my INSTRUMENT 1 to death and use it whenever possible. (Especially live on stage, where it’s a kickass controller for preventing “hey looka me I doin my taxes!” syndrome.)