Inspired by hebig’s post on the subject, I ran the user agent numbers for my RSS feeds (last 30 days of data). I also stole the nifty CSS bar graphs from the same location.

.bargraph { color:#555; background-color:transparent; text-align:right; padding:0 1px; margin:0 0 0 -1px; border:1px solid #555; }

.bartitle { padding:4px 0 0 2px; }

RSS Aggregators by percent of total requests
FeedOnFeeds/0.1
8.79%
MagpieRSS/0.3
7.64%
nntprss/0.4-alpha
6.33%
NetNewsWire Lite/1.0.2
6.01%
NetNewsWire/1.0.3
5.91%
Hep Messaging Library/0.0.2
4.56%
LWP::Simple/5.69
3.64%
NewsGet
3.57%
NetNewsWire/1.0.2
3.27%
SharpReader/0.9.1.0
3.14%
AmphetaDesk/0.93.1
2.94%
Shrook/1.04b
2.87%
NetNewsWire/1.0.3
2.54%
MagpieRSS/0.5
2.46%
Radio UserLand/8.0.8
2.34%
Syndirella/0.9b
1.88%
SharpReader/0.9.1.1
1.86%
Syndirella/0.91pre
1.74%
AmphetaDesk/0.93.1
1.49%
SharpReader/0.9.1.3
1.41%
Feedster Harvester/1.0;
1.37%
rssSearch Harvester/1.0;
1.35%
IdeaLibHttp
1.33%
Java1.4.0_03
1.25%
Java/1.4.1_01
1.24%
[not listed: 149 browsers]
8.32%