TLDR: Had one since launch and genuinely couldn't be happier with it.
The KSP is the main hub across all my gear. I'm running a midi out to my Hermod (so use track 1 as the main input to that and subsequently my massive eurorack setup), the clock out is plugged into Pam's New Workout and I use the KSP's other midi out over to my SH01a, JU06a, JP08, TB03 and Elektron Digitakt, Samples and Cycles. If I'm using it, I also send the reset out from KSP to MI Grid to restart that in sync.
When I hit transport on the KSP, everything else starts and stops (and resets) in solid time.
For what it cost, I honestly love it, it does everything I need it to do (and a bit more), has a decent amount of keys, I don't dislike the size/spacing of the keys (I'm not an expressive keys player but it totally does for my style/ability).
Sure, sometimes I'll run into the very occasional weird note that's in slightly the wrong place or forget to save but there's not that much in there for me to complain about.
The other night I needed to recalibrate an osc and checked the cv outs with a meter and got perfect, solid voltages that I'd expect to read at those intervals.
A few of the things I've seen criticism about seem to have pretty easy solutions to me - 'you can't record the arps': no but you can just program a sequence witht he notes you want in the order/length you want? - 'No global transpose' - just copy your pattern to a new pattern, transpose it and switch between patterns globally etc. 'Some scales include the wrong notes' - just don't play the notes you don't want right?
Compared to something like Soundmachines ((arches)) which I was stupid enough to kickstart to the value of something like €770 which now sits as a poor build quality, literally half finished and abandoned 'product' that lives in a box getting dusty under a desk in my studio, the KSP is a total delight. Soundmachines actually gave up on any updates and abandoned their own hosted forums for a year and then just flat out deleted them which I suppose is one way to deal with a less than happy userbase. Class act (they changed their name and have spent the last year hyping up an electronic recorder instrument on kickstarter which I have every faith will also be a piece of utter tepid half supported garbage to the disappointment of their many, fooled backers).
PS: I don't use USB/computer stuff alongside my physical stuff so perhaps some of the gripes are to do with that complexity but it's always going to exist. FWIW, the same thing happened with the BSP where people that were trying to do EVERYTHING with it were hitting the limitations so I can't speak for that experience of the KSP.
PPS: Totally not affiliated or sponsored by Arturia in any way, just a totally regular customer.
PPPS: If Arturia want to start sending me stuff for free, I'll be more than happy to become a shill kthnx.