I chose the 73 keys version... after years of 61 I wanted to expand my
range a bit (useful for those mega-splits, I thought).
My thoughts so far:
1. Korg's strategy of mini- stuff is a win: I was sold again on the whole
concept of hardware workstation after years of computers and VSTs by the
microKorg XL. I was so delighted by it, both as an instrument and as an
object that I bought myself microSTATION, microARRANGER and
microPIANO (for the living room y'know

just a step away ("oh it's a bigger, better microSTATION");
2. The keybed isn't that bad for me but hey... I'm one of those that like
micro- keys a lot. Definitely not a pianist

3. The sounds are very good for me, including pianos... in general I don't
care much for the "perfect" something, I just want character and
tweakability and those sounds got both. If I really need I could easily
reach for my iPad/iPhone and drive iGrand Piano via MIDI but I usually
prefer onboard sounds.
4. Strangely, I find presets to be quite bland and uninspiring... much worse
than the microSTATION... that's not a real problem with a Korg workstation
as you're supposed to tweak your sounds, but still....!
5. Speaking about tweaking sounds the relatively big touchscreen is a godsend.
I don't like, in general, using external editors, so having all
those parameters just in front of you, as opposed as hidden in submenus
like the microSTATION really leads you to better programming.
In a nutshell, was it a good decision to buy it instead of a Krome?
I think it was: I got myself a 73 for 20% less than the price of a Krome 61;
I can live without Krome's better piano, as I find M50's samples perfectly
serviceanle, especially if tweaked to my tastes: in a live mix it doesn't
make a huge difference, anyway, and in studio I could easily use a vst,
if I felt the need.
-- Federico