I'm a Linux advocate myself. My servers run Linux. I use Linux primarily for my work. At home, I either use Linux or my iMac. While I can get all the services I'm happy with, I have to realize that some people like services that are harder to find and host with Linux. I've come across my second situation recently where someone wanted a hosted exchange server. Some might advocate attempting a non-Microsoft work alike for this but I find there comes a point when it's more work than it's worth. This is especially true when you can set up a service like Sharepoint hosting for as little as $8.95 per month.
SherWeb provides a complete package with their Microsoft Sharepoint hosting. In addition to email, you can set up calendars, contact lists, tasks, alerts, rss feeds and a few other things. The rss feeds, for instance, can be connected to any of the Sharepoint features. You can create an rss feed for a contact list or calendar, and then allow certain users access to that rss feed. There is also a way to work on office documents with the document workspace hosted and shared. Another exciting feature for many business users, is the option to connect to, modify, and and new content with a mobile device.
All of these features are sharable with an unlimited number of users. You can add unlimited users to your system no matter which data plan you choose. Furthermore, all the features of Sharepoint are included with every data plan. The more expensive plans simply allow you more disk space. You can relatively cheaply try out all the benefits and then spend more as you grow.