I started playing UO again because of the KR client. When I first started back I used the KR client exclusively. As time went on I slowly migrated to the 2D client and now I only play the 2D client. I rarely log into KR at all anymore.
Although there are a lot of nice improvements on the KR client I think EA went to far in trying to improve UO without taking into account a lot of the features that the 2D client offers. They also sent it out way to early. The client still plays clunky even after many patches.
You can't use UOAssist or UOAutoMap with the KR client. Those two applications are so ingrained into UO play I have a hard time playing without them. Although the KR client tries to incorporate some of the features of UOA and UOAM it doesn't come close.
I'm not sure why EA went to such extremes with the KR client. They could have started with upgrading the UO client in stages. Beginning with the interface (I really like the hotbar, and chat on the KR client). Then, after the interface is mostly bug free, work on the graphics gradually.
From what I have seen since I have been playing UO again is the same issues they had when I played it long ago. A lacking infrastructure that has yet to address problems on a timely basis. Also the length of time it takes for expansions. UO is still, to this day, probably one of the most unfriendly online games there is. It's a real shame to because it's also one of the most in-depth, immersive online games ever made.