I have been trying to get PEAR::mail to successfully deliver emails to hotmail users without being flagged as SPAM and ending up in the junk folder, i have no problems with
I have always used PHPMailer in my projects, and what I did to avoid Hotmail's junk folder was to call a method they had that added MS Headers to the message.
Take a look at the source, and add those headers yourself.
Also, I recommend including a text-version if you're sending HTML e-mail.