I've used Google Reader since pretty early on -- not because it was the best feed reader, but because it was the glue between apps. Originally, I used it as the backend to keep the feed reader I used at work with the feed reader I used at home (for a while that was RSS Bandit, then maybe NetNewsWire.)
Once the iPhone came out, it was core to keeping feeds on your phone in sync with feeds on your desktop. And while I know developers had issues with its idiosyncrasies, it worked for me. Eventually, I moved to using Google Reader itself (and it's magic j-k keys) when I was on a computer, and a variety of apps on the iPhone/iPad.
Google Reader had this nice trends feature where it would tell you how much you read, and when, and which feeds were inactive (super handy for pruning dead feeds or finding those that had moved). It claims I've read 300k+ entries since October of 2010, almost 11k in the last 30 days.
I'm probably not a top 1% Google Reader user, but I bet I'm a top 10% Google Reader user.
And even still, I don't begrudge them their right to kill the product. All they get out of it (at least with me) is me using their ecosystem. I use Gmail (well, sort of -- my mail is there, I read it in other apps), I use search, I use Google Reader. Gmail and search are far more monetizable than Google Reader (i.e. it's much easier to put ad inventory next to what I'm looking at). Reader doesn't easily fit into the Google+ social play (though, really, does anything really fit into Google+).
So it's dead, and I'll move onto other options like Feedly. Or eventually to a paid service where someone will give me a nice tool for a couple of bucks a month. No big deal.
The real interesting question is "what will Google kill next?"
The most obvious answer to me would be Blogger/Blogspot. They don't monetize it (to my knowledge); it reproduces technology that is now in Google+; and it has to require a lot of care and feeding to keep it up and running happily. It's a mini-social network with webhosting. They likely have support folk hanging around to answer questions and make sure stuff is working.
Don't get comfy, Blogger users. You might want to see about importing your site into wordpress.com (or moving to your own hosted site!) in the short-term, just in case.
Actually, the thing Google is most likely to kill next is the goodwill of their brand. But hopefully it'll take them a few years to do that, as I've got a bet going about the size of Google ten years from now.