I have an HP desktop and a MacBook air and it's true. Firefox never crashes on my HP but it crashes several times a day on my MacBook. I also use Matlab quite a bit and I've almost given up on using Matlab on my MacBook. The only reason I use a MacBook is because I work in coffee shops and libraries a lot and it has the best weight to screen size ratio. Also, the wireless on the MacBook sucks. If I happen to sit in a coffee shop that hasn't upgraded the firmware on their wireless router, I can't get onto the Internet. I have a 6 year old Sony laptop that can connect where the MacBook can't.

As for formats, I guess the only place where it would matter is for pure text files. For some archaic reason, new lines are handled differently in Linux, Mac and Windows. If you open text files from other OSs in TextEdit in Mac or WordPad in Windows, it shouldn't matter too much. With emacs in Linux, you actually have to know the commands to convert between the formats, but if you're already a Linux user, you probably knew that already.