Although it is a good sign, it's not that cool. The operating overhead of a charity should be largely irrelevant to working out if it is a good charity.

For example, given charities X and Y both distributing anti-malaria pills (or something). X and Y are identical except X has operating overheads of 80%, and distributes 50 pills per dollar donated and Y has no operating overhead, but only manage 20 pills per dollar donated.

Clearly X is the better charity, since it moves more pills, even though only 20% of the donations it receives get through.

What I'm trying to say is: operating overhead is a poor metric for comparing charities, since the thing that matters is the final outcome given a certain donation amount.

(That said having a high overhead is probably a sign that a charity could improve, and so do more good per dollar.)