No luck here with 2.0.1 but I did get my POP3 issue resolved. I can at least send and receive now with Bizmail again although it feels crippled compared to the IMAP experience.
In regards to IMAP the CSR at Yahoo I spoke with told me that although IMAP for Bizmail was perhaps not official the reason it stopped working wasn't intentional on Yahoo's part but was because they are moving to the Zimba servers and it may have gotten fudged in the process. As far as he knows they are working to restore that functionality.
I told him that he should post that info back here or to the Yahoo Mail Blog since everyone now is upset but only speculating but he told me that he really couldn't (understandably) but would pass the info along internally to see if they could get something up about the status and what will happen.
It's hard to know if what he said (about them possibly restoring it) is actually the case or not. He was also speculating on it... but at least he may have a little more info than we do.
If anyone would like to make any comments in the meantime I suggest contacting one of the contributors to the Yahoo! Mail Blog. They seem to be the official place for Yahoo! Mail updates and perhaps may have some push with regards to Bizmail IMAP support on iPhone (and any platform for that sake).
The address for the Yahoo! Mail Blog is
http://www.ymailblog.com/blog/
The RSS feed is also available here
http://feeds.feedburner.com/ymailblog
Cheers,
Jordan