Windows 8 Pro upgrade for $40
Hopefully we'll get the same offer in the uk as that makes for a nice cheap upgrade path. Mind you its about time that Microsoft started making upgrades cheaper as its in their interest to get users running the latest version of their software. When it's £100 to upgrade it puts most users off as its verging on cheaper to buy a new computer than upgrade an existing one. It's even more of a problem if you have several windows computers/laptops in your home as the upgrade cost could run into hundreds of pounds.
£30 would make the update a no-brainier as far as I'm concerned though.