i've never really seen the sense of the sheldon method, to be honest. i use a pitbull mini-u for short stays, and try wherever possible to lock through the triangle and the front wheel, on the basis that it's marginally easier to remove the front wheel than the rear. you need a relatively slim pole for this (parking sign or construction, both plentiful in nyc). for longer stays (which are rare) i use the kryptonite fahgedaboutit chain and disc lock, chain through both wheels and triangle. i usually only carry one or the other, depending on what my plans for the day are. for overnight locking up, i trust only one lock, and that's on the door of my apartment.

edit: and yes, the lock is far stronger than the street sign pole it's attached to, but i think even in new york someone hacking down a street sign and then removing a bike attached to it, lock and all, would draw attention.