Great work. Now that I even found how to resize fonts in feed content window here and in the three view window here...
Just a simple idea: when exporting OPML, you might indent it a little bit to make it human readable, rather that one big line like now.
Also, about the font size: CTRL + and CTRL - (like firefox) could be nice. I have a laptop (so CTRL scroll up and down is not really convenient).
It's not a very important feature, I know. Just an idea.