Reading through all of these replies, it's clear that tensioning wheels is no longer universally understood or practiced in a lot of bike shops these days. What do these shops do before they deliver a new bike to a customer? They don't check wheel true and spoke tension any more? Very few wheels come perfect right out of the box, especially with today's machine-built wheels.

It makes a huge difference in how strong the wheel is, so anyone thinking it's not important is hopefully just cruising around their neighborhood. If you're going to tour coast to coast, carrying a lot of weight or want to go bombing down a mountain trail, you need good strong wheels and that means properly tensioned spokes.

I personally don't perform this myself. I have an experienced wheelbuilder at our LBS and he does a great job on all of my wheelsets, including building new ones. If he left I would have to find another bike shop.