If you own a business then in all honesty it can be both a benefit and a burden; therefore it should be carefully considered when selecting your phone lines. If you think that VoIP (Voice over Internet Protocol) is guaranteed to be cheaper, then I assure you that is not necessarily the case. You have to consider the set up costs.
The items required include hardware such as VoIP phones, an interface box (FXO, telephone system, SIP gateway, etc), network cabling ports (CAT5e/6 data points/sockets) and a network switch with PoE (Power over Ethernet). You'll need hardware, but you'll also need an expert to install the services on the equipment.
There are companies out there who can do this for you, but you become very reliant on their skills and availability should something go wrong or need to be changed in any way. Not only are you at the mercy of your specialist technicians, you also rely on the SIP/VoIP providers server to provide reliable traffic to your gear, as well as the ISP (Internet Service Provider) giving you a connection speed and quality of service that can support the bandwidth requirements.
It is often the case that a separate ADSL connection will be required to ensure it doesn't throttle the other network traffic. If your ADSL goes down or starts dropping out, so will your lines. Nothing like no internet AND no phones to get a business running efficiently!!
In saying all this, there are benefits and cost savings, but at the end of the day you must weigh up the pros and cons of moving away from the traditional telephone exchange lines that are by far more reliable and easier to remedy if required. There are many great deals for your billing services and prices per call on exchange lines have never been cheaper if you shop around.
Basically, its a case of buyer beware; be a wise consumer and if you are utterly void of technical expertise then you will save money in the long run by waiting for the technology to simplify and become more reliable and mainstream.