Cat Driver,
An overhead departure makes no sense at all usually. But it's perhaps fairly useful for student pilots who have difficulty understanding nav; I remember on my qualifying cross country getting very confused because a power station a few miles away wasn't where it should be. Just flying was enough for me at the time without working that out; I worried for several miles until I realised my heading was working, and only realised afterwards on the ground what had happened. But for anyone with even a minimal amount of experience it makes no sense at all.
Overhead joins I have mixed feelings about. It does mean you can circle around in safety and work out how to join the circuit, which can be very useful for the inexperienced, especially those of us with spatial perception difficulties. <img src="eek.gif" border="0"> I used to always do it, for that very reason. Also, there are a lot of quite busy airfields in the UK with only A/G radio. Some would say that it makes sense to have everyone joining those overhead, well out of the way, descending deadside etc, rather than having them all joining the circuit where they feel like it. I'm not sure, since it means the whole world can theoretically be flying around overhead at 2000 ft in any direction. I do remember one time when it made a lot of sense; I arrived at Shoreham at the same moment as an aircraft making an emergency (or do I mean precautionary) landing after a vibration problem mid-channel. I'd been earlier told I could join the circuit etc, but I saw what was happening, asked if I should wait as I could see all the fire engines etc and knew they wouldn't want anyone else around. I then circled overhead until the aircraft landed safely before asking if I could now descend. Probably easier for both me and ATC then anything else, under the circumstances.
But do we get too hung up on overhead departures and joins? Yes, definitely. And getting asked to join overhead in a helicopter makes no sense whatsoever - and it happens! <img src="eek.gif" border="0">