I play KR maybe 5% of the time I play and the rest, 95%, I do in 2d.
There are many things which are good in KR, but these should have been put into the 2d client instead of making an KR client.
The main reason I do not play KR is the inability to use the legacy backpack, it's just totally screwed up, the inability to figure out when I can start running again while stealthing, the inability to resize every container instead of resizing the whole UI, the crafting gumps are horrible, most items looking totally out of place, too big and just blurry, movement of character, wearable grafics .......
What I do like is mainly the big map, the ability to mark crafted items as quest items upon crafting (I never used it though), the macro hot bar, the infos about dci, hci, lrc, the spell effects, many monster grafics and some more stuff.
All in all the bad parts of KR are more significant to me than the good parts of it.