This. If Google went poof tomorrow, the lack of Reader would be the one thing that would leave me bereft. On the iPhone, I use mobileRSS as the UI, but I use the web app directly on the desktop.
I assume the OP question was to establish whether one would use something else, and Plus integration would definitely affect my answer. If there was a tight integration (like, share to a particular circle) I would be less tempted to jump ship, but I have to say I am more wedded to Reader that any other Google product simply because by searching the "Shared" section I can find almost every single thing I have found interesting on the web [I share to one person only, either directly from the RSS feed or to Reader using Shareaholic].
I assume the OP question was to establish whether one would use something else, and Plus integration would definitely affect my answer. If there was a tight integration (like, share to a particular circle) I would be less tempted to jump ship, but I have to say I am more wedded to Reader that any other Google product simply because by searching the "Shared" section I can find almost every single thing I have found interesting on the web [I share to one person only, either directly from the RSS feed or to Reader using Shareaholic].