I love building wheels... it is a meditative process and wonderful to see a wheel come together and for the most part, nearly every wheel I ride on has been built with my own hands and a bunch of folks ride around on wheels that have come out of my shop.
It is also nice to be able to build those wheels you just can't buy off the peg... because of this I have built a lot of 26 inch mtb wheels with SA hubs for winter riders and run a 1964 SS AG on my own winter bike.
I acquired a good number of 650A Mavic rims and have been very pleased at how nicely these work with vintage Raleigh bicycles... they are a little unique.