What's inefficient about a shell command?
I think inefficient was probably the wrong choice of words. It's not simple. For a lot of users, just being able to display the time and date with GeekTool is more effort than they care to spend time doing. Trust me, those who understand the shell (even just enough for the simplest of tasks) are far outnumbered by those who don't out there in the real world.
OP: Make it fully customizable, able to display the time, date, calendar (customizable, i.e.: number of months displayed, first day of the week, maybe even highlight dates with important events?), and maybe things like newest email messages, iCal events/tasks, etc, and you might even sway me. I'm perfectly capable of figuring out GeekTool, but I can't help but think that if there was an easier way that was still flexible enough to make it look like I want it instead of forcing me into a specific layout (here's looking at you, Stattoo), I would probably jump ship immediately.
Only trick is I wouldn't imagine a large number of people paying for it, though maybe you could take a page from the App Store and charge $.99 for it, might get a lot of people interested that way.
jW