I know just a little bit about Photoshop so I'll offer an opinion here. The differences between the current version of Photoshop, Creative Cloud and CS6, (which are basically the same thing) versus CS2 are monumental. There's no contest between the two. I could go on forever discussing the advantages.
With that said, many screen printers, especially those who aren't high-end art intensive and depend on Photoshop along with the fastest computers can easily get by with an old copy of Photoshop CS2 for image enhancement, separations, etc. Newer Windows systems will run it if setting CS2 to load in compatibility mode for Windows 7, Vista or XP. I have tested Photoshop CS2 on Windows 8 and did get it working properly.
Macs however are a different story and I believe the last OS X version Photoshop CS2 is compatible with is Snow Leopard running Rosetta, which permits Power PC coded applications to run on Intel based Macs.
In fact, I continue to use Adobe GoLive CS2 on a Windows 8 system to work on my websites without issue. Why? Because its simple, I know it like the back of my hand and my sites don't need to be very complex.