Final Cut Pro X and 7 on same system

I am using Final Cut Pro 7 and I was not very keen on Final Cut Pro X when I tried it out.

However, I have just learned that it could be advantageous workwise if I am prepared to work on some FCPX projects.

I'm just curious to know if it is safe to run both applications on the same system; e.g. do they share preference files? Do they use the same plugins folder etc.?

I know that in the past (and I mean the distant past) I have had problems trying to run different versions of the same software in the same machine and I'm too comfortable with FCP7 to just leap into working with an application about which I got an unfavourable impression and which many fellow professionals have told me instigated a move to Premiere.

Can somebody give me some definitive advice, please?