Right, so if a wallet exists in multiple places it *will* synchronize?
If a new address were generated on your laptop, it would be hidden from your view and kept in reserve, but it would eventually appear in your receiving addresses list (on your laptop) after you create 100 new addresses. And you won't have a copy of it (private key corresponding to the new address) on your desktop. So what I would do is to assume that one of the wallets are the master, and copy it to other devices at an interval, like every month or so. This isn't the same as synchronization though.
I put a copy of my wallet on my laptop and am careful not to double spend
How do you
prevent avoid double spending? I have to try it on my N900. :-)