I think it's undeniable that someone with a working knowledge of the command line can get things done much more quickly than someone without, especially as it doesn't preclude using a well-designed GUI when it makes the job easier.

The time you're talking about wasting is really negligible (imho). At the most a couple of days of actual use to get the basics. It'll pay you back in spades when you want to rename hundreds of files in a photo album (for example).

Jan