well, if I click on the link to your sitefeed suleiman, I just get to your site, nothing else happens, when it should ask me for my favorite feedreader...
same happens to me...
one strange littel story, maybe it is related to the problem you reported about your sites loading slow:
today I tried with the instructions you gave by mail to set up my mainblog site like yours, same theme (modified a little..) I tried to use the rss widget to display recent posts by showing the sitewide feed on my mainblog. I realized my server got slower and I got severall warnings from my system ... I had a look at the system resources and apaches children maxed out, mysql was going like crazy, a lot of slow queries , the system started swapping out and it almost came to a standstill...
I tried a tail -f /var/log/accesslog which shows me in realtime what apache queries are incoming and 90% of those where accessing the sitewide feed... when I took out those feeds from my mainblog and reloaded apache everything went back to normal, so as I remember you reporting your site being slow... you might check these issues.
I am not sure where the problem comes from, but I can for sure demonstrate and proof that if I put up my sitewide feed on my mainpage and relaod my site severall times the system breaks down.
maybe someone with more insight into these matters could give me some hints what to check?
oh and by the way, does this plugin need something like this:
RewriteCond %{REQUEST_URI} ^/wpmu-feed/(.*)$
RewriteRule ^.*$ - [L]
like mentioned a few posts above mine?