DC/DC convertor: to isolate grounds or not

[burningman]

I was wondering if there are any benefits to using isolated grounds available with DC/DC converters. Here I am thinking of building a circuit that has its power ground completely isolated from audio ground common. The audio common would be chassis grounded, while the power ground would be rectified/filtered and plugged directly into the Vin and GND of the DC/DC converter without any connection to chassis or audio common. The two grounds would be completely separated from each other by the DC/DC converter.
Would it be better practice to connect these at one point as opposed to keeping the power ground 'floating' (for lack of a better word).
Thanks.

[brett]

In my limited experience it doesn't hurt to leave the power ground floating, EXCEPT that you need a grounded chassis wrt the mains or any dangerously high voltage (50V and up).  Back-to back transformers are often left floating.
someone should know more.

[burningman]

Any other thoughts?