First of all - If you are using another page coding than UTF-8 (e.g. iso-8859-2) you won't see your national characters in rss feeds (changing records in ijoomla_rss.php from UTF-8 on iso brings no effects). If you had a problem with e.g. Jom Comment - you will have a problem with ijoomla RSS Feeder too. It's this same problem.
Second - If you have the categories and sections name in other language than english (e.g. with characters in iso-8859-2) the Feed Burner will not recognize it and you won't turn it on in ijoomla RSS Feed admin page.
And the third problem - If you choose "Show Feeds URL" on your admin page in "ijoomla RSS Feeder Configuration" and click "Preview" on any categories you will see an error "Notice: Undefined variable: b in /home/.../administrator/components/com_ijoomla_rss/preview_rss.php on line 865" (you can see it on ijoomla demo page too). The support of ijoomla.com helped me removing the notice message, but when I removed RSS Feeder and installed it again on this same domain, the error showed again.
I think, that is all, but I'm still trying. It's very good component but needs a time Regards for all ijoomla.com team.