Over the weekend I went on a bit of a coding binge and implemented event block overlap in Scooby's 'timed' events (events that have a start and end time -- not 'all day').
It's a clone of the implementation in Chandler -- some really elegant algorithms for both the block indentation and width calculations written in Python by Alec Flett, one of my co-workers at OSAF.
I don't know Python (although I have read O'Reilly's Learning Python book), so I had anticipated this would take a week or longer to work out completely. It's proof of Python's simplicity and readability that I was able to knock out a basic implementation over the weekend.
That leaves recurrence and tiling of all-day events to finish up before Scooby will be close to anything that people can actually use -- but getting this overlap stuff working is a pretty big step.