I am just setting up a business (well two actually) and I have decided to manage the phones using skype, dispensing with landlines altogether. I may live to regret this, but I thought I would share my reasons.
Alongside computer to computer calls, Skype also has a feature called a Skype-In number where users get a phone number which can be rung from any landline or mobile. I can therefore give out a number on my business website etc. which goes directly into skype. Skype also provides voicemail and call forwarding at very reasonable rates.
These numbers are pretty cheap (£35 per year + VAT, or £16 if you join Skype pro which is £1.50/month). The other option I had was to get a landline at £15/month + calls.
Convenient: Pick up calls from any computer
I use my computer at home and at work, and my skype calls are routed to the terminal which I have open at any time. This means that calls are automatically directed to where I am.
Multiple phone numbers from the same location
It is possible to have more than one skype-in number running off the same skype account. The only downside here is skype does not tell you which number has been rung.
Quality of skype calls can still be an issue