If you are going to spend the money on an external meter then make it worth while and spend a little more on one that does spot metering too.
Although if you have a built in meter on the camera and especially if it's digi then there really is no need, unless you want another gadget to slow down your picture taking.
If I'm shooting somewhere with film and the EOS, I'll often just use the canon for metering and fire off a shot to look at the histogram/preview.
Although, if you want to look the business you can't beat emerging from under the darkcloth and looking at the meter with a knowing nod. :eyesup: :lol: