Yes, I have done a lot with 3Com VOIP. It is a layer 2 layer 3 phone system. That has 2 versions.
The 3Com NBX is a nice system in a box. Functionality is good and voice quality is good. It is an all around good solution as long as you do not want anything too fancy. It supports multiple sites via a proprietary VTL system.
The 3Com VCX is a large market system that is working its way down to small markets. It is very flexable and redundant but is not as easy to configure as the NBX,