How long should it take for a domain name to be transferred from one hosting company to another?
As long as the domain is unlocked, it should take anywhere from 48 hours to about 7 days, usually more towards the 7 day end of the scale. It also depends on the hosting companies you are moving from and to (moving from any Yahoo! hosting is almost guaranteed to be 7 days).
Would you be willing to expand on that last point a bit? I currently have a domain hosted by Yahoo that I would rather like to move to some other company (not that Yahoo haven’t been keeping it up and running fine, but there are other issues) and I have been putting it off because I do not know how much hassle it will involve, or, really, how to go about it. It sounds like you may have some relevant experience.