I have been searching for a reliable PST conversion tool for some time. Apparently until last week I was looking in the wrong places! Emailchemy certainly has resolved that issue. This handy application can handle a vast number of mailbox formats across Macs, Windows and Linux/Unix. It can write to 7 formats that support dozens of email clients across the aforementioned platforms.
In my case I took a 450 MB Outlook archive PST file spanning 24 months and used Emailchemy to import the messages and mailbox hierarchy into Mail.app on a Mac running Snow Leopard. Processed 3500 messages in less than 30 seconds. There are a number of options including handling attachments.
For $30 - this was not a difficult decision considering I now have this critical history of email integrated into Mail.app and my backup workflow. There are options for household and business use - though the Emailchemy site does not provide pricing for email migrations. Contact the provider for more information and pricing for your needs.
An interesting option for those looking to simply preserve messaging but not integrate into an email client - there is a conversion to CSV file option.