Taking another look at this since some time has passed and to see if any improvements were implemented. I was reminded about this after reading a GHacks article mentioning that he used QuiteRSS as his default RSS Reader. Here are some initial observations as compared to RSSOwl, which is my default RSS reader:
Importing feeds and CPU usage:
I have about 5000 feeds to import using an OPML file. When I tested this on XP SP3 32-bit before, it tied up the system with high CPU usage, which was surprising. That hasn't changed much. The problem is that it attempts to update the feeds as it imports them. CPU usage stays at about 100% whenever the feeds update, even for feeds already in the database. For 5000 feeds, this takes over 30 minutes to complete on my system. RSSOwl can import feeds without updating them immediately, with CPU usage typically about 12-18% while updating feeds. I went ahead and completed the import to evaluate any additional performance and feature improvements.
Groups of feeds can now be deleted by folder; they can also be imported - that is an improvement. It doesn't appear however that feed groups can be exported. I also tried to import labels and that didn't work.
Good once all the feeds are imported. Responsive interface, as good or better than RSSOwl.
RSSQuite does have basic filtering, which I don't think it had before, but what it has should be enough for the typical user. It doesn't have as many as RSSOwl, which has numerous filtering options for individual feeds and groups.
RSSQuite - Outstanding internal browser. Up-to-date, fast and comes with a built-in AdBlocker and Flash-blocker. Videos and audio can be played/downloaded right from the feed window.
RSSOwl - Not as good as RSSQuite for sure. Because it uses the system's IE engine, if using XP with IE8, there is going to be problems, especially with multimedia.
I would describe the interface as functional and somewhat plain looking as compared to RSSOwl's elegant interface. It can be tweaked to change fonts, colors, icons, style-sheets, etc. to make it more usable, whereas RSSOwl's interface looks great right out of the box. I'm still playing around with the interface settings.
Although I have portable versions on a separate partition that I sync with USBs; on a daily basis, I use the installed versions. I measured the total sizes by adding up all the related files for each reader for the installed versions with HDDB. This is probably not a good comparison, but it does provide an idea how big these apps can get.
RSSQuite - 200MB installed with 5000 feeds (newly installed, will monitor to see if this grows with time)
RSSOwl - 3.0 GB installed with 5000 feeds (a lot of this may be cache, java files, and backups)
Each has it's strengths and weaknesses. The choice between the two depends on how they are to be used. To me, RSSOwl would be a better choice on desktops where sophisticated filtering is needed for thousands of feeds. QuiteRSS would win out in a portable environment because of its smaller size, performance and compatibility. QuiteRSS also seems to be frequently updated, much more so than RSSOwl, so it's probably going to continue to improve.
I haven't yet tested these two apps on a system with higher-end HW and Win7 yet. I'll post the results if anything significantly different is found.