Most players in the VOIP world aren't even worth looking at. The two primary players are Cisco and 3com. But there is something that you DEFINATELY need to be aware of.
Many phone systems are beginning to say that they provide "IP phone systems". Northern (Nortel) is a prime example. In reality, they DO NOT provide a true IP system. What they have done is add an IP card to their PBX system, allowing their PBX to be used over an IP network. You still have all the flaws of the traditional PBX systems, with the added challenges of trying to convert that to an IP network. Stay away from any IP phone system which has been converted from a PBX. Companies like Northern have spent millions on R&D over the years for their PBX systems, and can't afford to throw all that away to move into the IP arena. So they've simply adapted what they've done with PBXs and integrated IP functionality.
If you are looking for a TRUE IP system engineered only to be an IP system, Cisco and 3com come into play. I've worked with both, and while they may be powerful, both have a tremendous learning curve and are overly, and unnecessarily, expensive, complicated and cumbersome.
It was due to all these findings that I started some intensive research. I wanted a system that was truely IP, cost-effective, and most importantly, easy to implement and manage...and use. I also did not want to be restricted from doing anything. Unless it was completely feature-rich, I didn't want it. The product I fould is amazing. I've installed it in multiple locations, and it's all I recommend now. It may sound like I'm a salesman of the product, and while I'm not, I sure talk it up enough.
The system is manufactured by Shoretel (shoretel.com), previously known as Shoreline, and their product is second to none. You can read all the accolades on their site. They system runs on the VXworks OS, which is so reliable that it is used primarily in heart pacemakers.
Further questions? Just ask.
