Loads of problems across the world lol.

You'll probably have to look for updates for applications and/or additional drivers for the peripherals.
I know you've got your issue sorted now, but I thought I'd post my experiences here. They may help someone.

I had updated to Yosemite from Mavericks on my iMac and my Macbook Pro. Everything seemed OK except I couldn't print through the iProof PowerRIP to my Epson Stylus Photo 2100. Up to the upgrade everything worked fine.
I contacted iProof and they were very helpful, although there wasn't a way to make it work. It appears there are a few issues with Yosemite and add-ons/software. Apple were trying to get to the bottom of the problem, but it wasn't happening soon. I back-installed Mavericks to my MacBook from Time Machine and updated the RIP to v10 and it works perfectly again now. I'll just have to wait for Apple to catch up then go for Yosemite again.
Make sure you back everything up separately (not just on Time Machine) before back-installing!
A pain really, but workable.