I've used SQL Diagnostic manager since around 1999 ( in different owned guises and in different client sites )
It's an excellent tool for the DBA who needs some background assistance with tuning, optimisation, diagnostics and trending. Yes you can do almost everything yourself, after all it only does server side tracing, but when you need a new car you don't ( normally ) build it yourself you buy one already done .. having diagnostic manager frees up my time to be more productive , as a Production DBA, and keep on top of the systems. There are a few things it does that you would seriously struggle to handle yourself but these are only useful if you have problematic applications/servers, I can state that without some of these advanced features I would not have been able to resolve problems so fast - in financial production systems this is obviously critical.
I recommend DM to all my clients.
[font="Comic Sans MS"]The GrumpyOldDBA[/font]