I'm pretty happy with my K. Chose it over an F or X because the just slightly over G19 sized K is slightly easier to conceal, and I don't exactly need the longer grip in a 10-round state... at least unless/until Duncan v Bonta gets resolved.
Most of the changes have already been noted above... no more finger grooves, flared magwell, slightly improved trigger. The CA "features" are also done really well compared to some of the competition; a relatively unobtrusive LCI on the extractor, instead of the hole in the slide/barrel that on some other brands blows powder residue onto the optic; and a mag disconnect that doesn't get in the way too much, even if I do think it's silly that they are mandated. HKs designers seem to have found a way to do these without adding machining steps to the slide, barrel, or frame. Compare it to Walther's insanely over engineered system with that big cylinder, a hole in the frame, and several unique parts.
Other HK strengths: Not needing to pull the trigger to disassemble (which is also why the mag disconnect is less annoying than on some brands) is huge in a safety sense. The optics mounting system is much more robust than some others, and the OEM steel plates are better engineered and stronger than some of the aftermarket choices. And the magazines are solid and well designed and they all, standard capacity or 10-round, function reliably with defense ammo (unlike Glock 10-rounders until very recently, and anything Glock is a moot point in CA for now).
They aren't perfect, but most of the shortfalls are easy fixes if HK chooses to keep evolving. The grip texture is way too mild, I'd really like to see something closer to the more aggresive texture on the M&P or the PDP. This would be easy to do by offering another set of backstraps and side panels with a rougher texture. And I don't get why the iron sights on an optic ready pistol are so low, they aren't visible through my EPS which has one of the lower deck heights available. The tall sights on the long slides work well with the 407C and some other taller optics, but it would be nice to have OEM sights a little taller than now so that at least the lower deck height optics would co-witness.