Two Macbooks on different OS X

Hi, I have a 2009 Macbook Pro which came with Snow Leopard (which I like!)and which I use with a freestanding 24"Apple cinema screen mainly to process photos with Photoshop.

I'd like to buy an11" Macbook Air so I can download RAW files when I'm travelling abroad. I guess I'd like to use the internet and mail too. Would there be any issues in having two Macbooks with different operating systems? Would I have to upgrade to Mountain Lion on my old MacBook Pro? Could I transfer my RAW files from my Macbook Air to my Macbook Pro without incident?

Absolutely no problem using two Macs with different versions of OS X on them. The MBA wouldn't somehow mark the RAW (or any files) as only Mountain Lion specific and be unable to be used on the Snow Leopard based MBP..

So have at it..

Thank you so much! Every time I think of changing something or updating , I have a compatibility panic!!
Happy holiday from London, UK!!
Rosie

You might have compatibility issues if, for example, you wanted to run a particular application that was a Universal one and had not been made Mountain Lion compliant. Since PPC support was dropped in Lion, that application wouldn't run so now you'd have a problem sharing files between the two Macs that were created by this program..

But if you are just sharing generic things like RAW files or other standard formats, these are fine..