I was one of the power users. I fucking loved Google Reader.
Unfortunately, I don't really have anywhere else to go at this point.
UI aside, the biggest loss was that all of the content which I have shared over the years is now just gone.
Yes, I can view and download them with Takeout, but that's beside the point: it no longer exists with regard to Google Reader. I almost think it would have been better to just dump all of the shares into my Google+ stream automatically than to do this.
I like the idea of (and always rather expected) a circle specifically for Google Reader which would be populated with the people you were following and sharing to. Then the share functionality in Reader could have provided content for Plus while maintaining a great system already in place. There could even be a flag or button to share to other circles or publicly.
I don't think that the new changes are a complete lost cause. They should definitely be doing less grey (links aren't grey here; why are they on Reader?) in the UI, and the real estate for, you know, reading could be larger. I'm not going to pull up the stakes and leave just yet, but I'm not sure how much longer I'll stick with Reader for now.
Hate to do it, but if anyone knows of any other RSS aggregator with excellent UIs and some sort of sharing and bookmarking system, I'd be appreciative. Wonder how much work it would take to just make one for myself.