I coming from school where single long checkout form suppose to be the best idea. Back quite a few years ago I sold onepagecheckout.com domain for a chunk of cash.

Just 2 days ago I purchased very expensive laptop via multi page checkout process which I really appreciated.

The key was to remind customer what he is buying, all options, warranty, shipping etc - make sure the complicated configuration is delivered in clear way.

Gigantic one page thing would be less welcome