The concept is a very nice one, and what there is works well. But what is missing makes it more awkward to use than it should be.
The first thing I noticed was that you could add people to events by dragging, but there is no way to show their contact info in the event. You must go over to the address pane and find them. Hovering over their name in the event should display their contact info.
I couldn't find a way to delete an email from within crm4mac. I highlighted the mail, clicked on the "-", and was able to delete only the reference in crm4mac or all email references for that day. But only the references.
The window for reading the email is too small because of all the other panes, but you can't pop a full-screen view of the email without launching (or switching into) Apple Mail.
There is no option for displaying events and mail only from today forward unless you change the filter dates every day. All the default filters want to include the past week or month.
There is no help. There is no manual.
Bottom line? This has the potential to be a great product. And when it gets there, I expect to use it as my main interface and it will be well worth the $50. But it isn't there yet ;-(