Good : We can be contacted at any time
Bad : You are therefore expected to keep working all the time
I despised my works phone because whenever it rang I knew it might be some long query about some problems - or that I'd have to go in and fix summat. Though that stooped in 2006 when I retired.
After that I carried a phone everywhere in case my aged and feeble parents needed something, which I suppose was good actually. Then got a Blackberry so I'd get "push" email notifications from the cameras at mother's house in case she went wandering off and I'd have to go and rescue her, so that was a cause of some worry at times.
Very useful in the pub to find out some facts from t'interwebby rather than talking nonsense about some misremember facts.
Wouldn't like to be without one now though.