Columbus used to make a tubeset called 'Metax' that was stainless. You can still find some if you hunt around like a madman for it. It's not much different to work with than 'regular' steel, what the main limiting factor is is that you cannot brass braze to it - you have to silver braze. Silver brazing requires a closer fit as silver cannot fill gaps like brass can. This is less of an issue if you TIG weld the man tubes, but none-the-less it makes brazing on things like cable stops a pain - not exactly conducive to mass production.

Stainless is not heavier nor significantly diferrent to modern bike tubing. I have a suspicion that it might be more difficult to draw into butted tubing, but I'm just guessing.

Also, there are many companies that do stainless lugged bikes, which look awesome. Expect to pay over 3 grand just for a frame though - we're talking gourmet ***** here - hand polished by a grumpy artisan in a shed somewhere with a 6 month lead time. Good stuff.

Me personally, I've done some Nickel plated frames, but I bead blast them first so they come out looking a bit like titanium. I've even nickel plated a couple of Aluminium trials frames, but polished the areas where the decals would be, put the decals on, bead blasted the frame, removed decals, plated - you end up with a matt frame but with polished graphics. Freaks people out.