I was able to test iTunes 4.9 this morning and see what it does and how it does things. So much for being open... You can not add your own RSS feed into the application at all. Dave, as I am, will be asking where is the RSS in iTunes?
If you search for RSS in the help it turns up blank.
I was also not surprised to see they are not supporting BitTorrent at all, and for popular feeds like This Week In Tech who uses BT and Coral to deal with bandwidth issues of straight downloads, this is going to be somewhat of an issue. Just so you know, Coral has bandwidth limits, and routinely caps out with this feed -- how does Apple deal with that?
Update: If you drag a RSS enclosure feed to iTunes it will allow you to subscribe. It offers no auto-discovery, something August worked very hard on for iPodderX 3, to help with ease of use. Also feeds with a lot of text entries in them or all text seem to have issues in iTunes.