Keep in mind your total cost when changing tires. Living in Honolulu has it's own benefits (lots of sun, riding time, and those thong bikinis) Ahem, back to the subject at hand. After paying shipping and waiting about a week (or more since 9/11), and then paying for install, I find it is often better (read not cheaper) to have one of the local shops supply and install some parts. You may never have a problem with a mail ordered part (hell I have enough of them chrome ones), but on the major moving parts, I like to have someone who I can get to fix a problem with a part that they sold me.
Of course all of this may be no factor in your decision if you are not on an island with only 2 major dealerships and a handful of custom builders.