Since Mai 14, 2004, I’m using intensively Sauce Reader from Synop as feed-reader and I would like to summarize my impression, as an "evaluation phase conclusion" (for my other posts, have a look here, here and here) :
What’s Cool
 
Great user interface: clean, intuitive Outlook 2003 style user interface
 
Sauce Reader toolbar available in Internet Explorer
 
Very good usability
 
Since this version: performance, stability and a quite good memory foot-print
 
Customization of keyboard shortcuts
 
Great desktop alert when new feed items arrive
 
Feed discovery and one-click subscription to RSS and Atom feeds
 
Pop-up blocking, complete default browser support
 
Integrated weblogging environment with full posting functionality (including image uploading)
 
Great full-text search functionality (within archived items) 
 
Support for content in any language or character encoding
 
Automatic application updates
 
Support of proxy, great feature to stay tuned at work
 
Free for personal use, reasonnable price for commercial use ($25US per license)
 
Last but not least, very active development team, professional alpha- and beta-phase
Room for improvement
I’m still not totally convinced by the “posting” module. The development team improved a lot the possibilities, stability and performance. But I still prefer to use the very simple Blogger web interface. Perhaps out of habit? Let’s see. 
Conclusion
All in all, I still think that Sauce Reader is the best aggregator at this moment (on Microsoft platform). The last developments of this tool (five releases now!) give me a very convincing impression of the Synop’s capability and user orientation.
PS1: have a look at the reviews of Robert Scoble and of Laurent.
PS2: my review was linked by Synop on their product homepage ;-)