Choice between implementing domain/Exchange or something like Workgroupshare

So, at work we have always used a workgroup across the network and a bog standard shared drive, even though we could be running a domain.

The reason that we don't have a domain is that no-one here has the tech-know-how to set one up or maintain it, even though I see plenty of pros (for example) to having the email in-house instead of our current POP3 service.

But, the major benefit to configuring the Exchange server would be things like shared calendars, tasks, etc.

In researching this, I've come across some software that says it can offer all of these advantages without having Exchange set up. Has anyone ever heard of this http://www.softalkltd.com/products/workgroupshare/ Are the claims that they are making unrealistic?

Is it really that expensive to get someone in to set up an Exchange server, with something like a linux box for mail? Would there be an ongoing maintenance contract?

I'm here looking for advice from people that have been down this road before, would you have any pointers please?