I've been using SharpReader on a daily basis at work for a while now and it's usually performed fine. It's a bit of a memory hog for the ~100 feeds I have it monitoring currently, but it had never kept me from doing my work. Recently, though, it's started showing new items in the wrong folders, and this has got me looking to finally make the move to Bloglines as my main feed reader. I was thinking of using Thunderbird 1.0 in this role, but two things make that a non-starter: no support for importing my subscriptions OPML file (or OPML export, for that matter), and no easy way to toggle proxy server settings as I can with Firefox and SwitchProxy. I've synched my SharpReader subscriptions with it for a while now, so all I really have to get used to is Bloglines' interface. I think SharpReader's text display is more efficient, but Bloglines' accessibility and utility will probably make my feed reading more efficient and easy than before.
Another reason I'm moving away from SharpReader is the fact that it hasn't been updated to support RSS enclosures. As a Net-based app, Bloglines doesn't have settings for automatically downloading enclosures, but I'm using Doppler for that on my server, since I want to download my subscribed podcasts to only one location.
A happy by-product of shifting to Bloglines means that I can more easily read my feeds at home and other locations. I'll post about this again if I have any serious usability issues with Bloglines.