Stopped using a mob for following reasons:-
1. didn't have a contract and was spending £20 a month to retrieve voice mails
2. Customer where calling me up for silly things, e.g. I run on a booking system as in the customers know when I am coming to the hour, and was getting calls like "are you coming today?", "yes I was just driving up your street and had to pull over to answer this!"
3. Battery going and having to charge all the time was a pain
4. Having to go for topups was torture as well
now I know some of them problems would be fixed with a contract phone, but get free evening call on my landline and the voicemails are free, so I prefer a landline.
However do think it looks more proffessional as well.
If you like using a mobile, why not use both?