Definately establishes yourself as a legit company. You don't want customers calling your cell phone to have you pick up 'Hello?'. Even if it just rings a voicemail then that is good as well.
Check out Google Voice (free). You can get a cheap 1800 voicemail number and have it forward to your google voice number if you want (gvoice will even transcribe ur voicemails into text format and e-mail/text it to your phone!). Pretty neat service