Hilmar,
>I read somewhere that a function (or method) should have a single point of exit (RETURN). Is this considered a general design principle, that should usually be followed?
>I find that it is more complicated to code a function or method to have a single RETURN, but I also see that it may make cleanup (if required) easier.
IMO having one exit point is mure structured and easier to maintain. Especially for cleaning up (as you mentioned). In many cases I have to set something back, release an object or have to do anything else, before returning and I want to do this only in one place. If you first think, you won't need to clean up and you are enhancing your code later and then you have to, you will have to change a lot of your previous code.
Armin