Although I haven't done it, I'm pretty sure that you can set up Outlook (2010) to work with both SMTP/POP email and with Exchange simultaneously.
Here is the scenario: I work with a group of independent contractors and we want to have joint email, calendar and contacts for the work we do together - so we're thinking of using a hosted Exchange solution for this purpose. At the same time, we want to maintain our own individual personal/professional email/calendar/contacts using our respective SMTP/POP accounts.
If we are using Outlook, is it possible for these two to coincide peacefully? Are there any pitfalls or compromises involved here? Will Outlook happily show combined personal and exchange mail/contacts/calendars while keeping the personal stuff hidden from other Exchange users? Or will it be a matter of having distinct mail accounts and calendars that have to be selected one at a time on the left hand side, without any integrated view of inbox/calendar/contacts?