I'm one of only 5 IT bods on a 24/7 Silicon plant and we manage everything between us, VMS, MS Servers, Unix, Linux, Databases, Network, phones, PC's, even down to supporting the controllers in the machines in the Fab where we can, it is hectic at times but we manage.
The only thing I say is if you enjoy variety it's great, I think it probably makes you more valuable too.
If you are a bit of a dinosaur and will only do "what you do" it probably wouldn't be for you. And you wouldn't fit in in the team anyway, because unless we all help each other the way we do it here wouldn't work. I was taken on to support Promis/VMS but now I do it all so I guess you can teach old dogs new tricks.