Put me in the fan section...

Stainless will rust, eventually, very lightly on the surface. I've had it occur on non-bicycle items, and just barely noticably on the bike below. Something as simple as auto wax can protect it for a very long time though. These lines of stainless are harder than the stuff kitchen utensils are made of, the specs prove it as so. Scooper summed up the properties very well, but for me these were the selling points:

• It is very hard and can be drawn into thin tubes without great fear of denting
• It need not be painted, though it certainly can be
• A brushed finish can be refreshed, by me, at anytime with results much better than my paint touch up jobs
• Ride it hard, put it away wet, no problem
• Grey matches my hair

The rest of the benefits are true of any fine custom:

• The ride is sublime, tailored by the builder to your needs, not an off the rack carbon type of thing
• Dream it, they will build it
• If it is your dream bike, why not get it made of a material that has arguable benefits and a certain rarity