I personally haven't had any problems with the iTunes 7 program, but I have professionally. The DCD Records podcast I produce is in the new iTunes 7 podcast directory, but all of the programs listings have disappeared!
And unfortunately, iTunes holds podcasters at arm's length when it comes to fixing problems. Its not that difficult to do the original registration, but almost impossible to get any changes made to the feed, and there's no way to "open up the hood" and see what the problem might be with the iTunes program itself.
When you follow Ken's link, make sure you read the article's comments. Taken in conjunction with this posting from Macworld, it seems that a fair amount of the problems seem to be with Windows, or with third-party add-ons. In my case, we did change servers around the same time the new iTunes store launched, so that may have added to the problem.
I'll keep you posted on our postings. I'm not sure the Apple's rotten -- just a little bruised.