RSS feeds/ newsgroup subscription

We are planning an RSS feed but haven't implemented it yet.
I should have posted my information in this thread.

I googled for vBulletin RSS and pretty quickly saw somebody suggest that appending external.php?type=rss&forumids=xx,yy would provide RSS feeds.

I went to Google reader and added this as a subscription -- it seems to behave itself at least partially well. I think I got all the forum numbers.,4,21,11,5,18,13,19,8,9,14,15,16

Is there a problem with using that url?