I like to keep work in it's place..
I refused to take a blackberry; if I did take one, I'd be expected to be at work's beck and call 24x7 for every trivial little issue.
I like to be able to turn work off, so my company laptop is fine for me. If for some reason I really am needed outside of my usual hours, they can call me on my mobile and I'll fire up the laptop if it's important enough.
I know that others I work with have also turned down the offer of a blackberry for similar reasons and so this may be the case in other organisations. Perhaps this is another part of the reason why notebooks were found to be twice as popular as mobile devices for remote email, etc access.