Definitely when a shared ip is blacklisted then your emails will not be delivered and having a spf record will prevent spammers from abusing your domain, without a spf record hotmail, aol and others will not deliver the email to the inbox but rather the bulk/junk folder.

Before signing up with a host, ask them the ip that your site will be hosted on and then check it at http://www.dnsstuff.com/ under the Spam database lookup and that will avoid that problem.