PAE kernels do not run on non-PAE machines. Been bitten by this before. This is stated clearly in the article.
I found the comment "time to upgrade" in the article frankly offensive. We live in a world were disposable commodities and built in obsolescence cause pollution and impoverishment all over the world.
Ubuntu, the most popular system for open source thin client systems (LTSP). We have plenty of laptops which will now not work with the next version of Ubuntu which we run as thin clients. The Pentium M is a good mobile processor and completely suitable for a number of modern workloads. There are Pentium M desktops out there too.
Think of the impact of this on third world computing in the global south, were hardware more recent than 8 years old is "new". Ubuntu will really be stabbing Africa in the back with this move. It's not "time to upgrade" until most people have stopped using the hardware. Please don't obsolete a huge wedge of global computing resource.
Really glad I stuck with Debian on my systems.