Don't discount powdercoating. Whether its paint or powdercoat, the finish is only as good as the prep work done before the coating material was applied. Make sure the coater blasts off all the old coating and preps the bare metal before shooting it, and that they have experience with stuff that has odd angles (like the tight angles at the BB of a bicycle frame ). I've had a few bikes powdercoated and they turned out great and about 1/3 the price of painting. The attached pics are of a Schiwnn LeTour II I had powdercoated a few years ago due to its pretty beat-up paint job (it ran great, just looked like crap). Its still still looking good after serving as a year-round daily commuter. This was a basic job (no clearcoat, special additives).
FWIW: The refinishing decision varies depending on what I plan to do with a bike. If I had a bike I was going to keep and ride myself, and it had a crummy paint job, I'd get it refinished the next time I disassembled it for servicing. If it was a true vintage/collectors bike that I got for cheap and was just going to flip, I'd just clean it up, adjust everything, and post it 'for sale' since (as mentioned previously) collectors like 'em in original condition.