I came across this great solution which can get you most of the way there with your public folder support for legacy SharePoint 2003 to Exchange Online migration scenarios.  It's from a company named MessageOps (http://www.messageops.com/software/sharepoint-bridge) and the product is called SharePoint Bridge.  What it effectively allows you to do is move messages from a designated Exchange Online mailbox into a SharePoint Online document library.  Check it out at the link above.

A frequent question I receive is how to monitor the availability of BPOS and how to access BPOS service notifications.   There's a few good techniques and resources out there.  In my experience, BPOS availability has been great and I've only had one issue since August 2008 when I started using it. It cleared up within a minute or two.  Here's a couple of good tips:

Monitoring BPOS

There's a few different ways to monitor your BPOS service.  If you own a monitoring tool such as Solar Winds' IPMonitor (http://www.solarwinds.com/products/ipmonitor/) you can easily configure fairly sophisticated queries against your various BPOS service URLs such as SharePoint sites or OWA.  I generally configure some alerts againsts my SharePoint sites and OWA.  In the use of your BPOS service you also rely on either your own DNS hosting infrastructure or perhaps a third parties.  I set up QoS monitoring on all my DNS servers - remember if DNS is not working properly mail flow, your website and other services may not function as you have designed.  You can also probably monitor SMTP by configuring a dedicated user (consuming a license) and using an SMTP monitoring rule that can be configured to support authentication (these are available in the IPMonitor product). 

BPOS Service Notifications

BPOS Service Notifications are another great way to keep in touch with Microsoft annouced service issues or maintenance. 

North America Microsoft Online Services Standard RSS Feed https://rss.microsoftonline.com/

APAC Microsoft Online Services Standard RSS Feed https://rss.apac.microsoftonline.com/

Europe Microsoft Online Services Standard RSS Feed https://rss.emea.microsoftonline.com/ 

Message Filtering RSS Feed http://rss.messaging.microsoft.com/ 

Creating resources such as projectors, conference rooms, or training areas helps reduce double booking and other conflicts.  Exchange Online Services through your BPOS account by Microsoft Online Services allows you to create a shared resource such as a conference room or projector.  Doing so is easy and once created these resources can be seen in both the Outlook desktop client in the calender area as well as in Outlook Web Access (OWA) by setting up a new meeting, adding the resource as an attend and checking the associated free/busy information. 

Here's a short screencast on how to create the resource object in Exchange Online Services.