The Inter-Tel Axxess does work very well in an Executive Suite environment. The VPU applications allow multiple auto attendants and calls can easily be labeled with company names.
ALSO - with the OAI/CTI interface, you can enhance the Executive Suite application. Here's a link to a company that developed a vertical application for Executive Suites, even back office operations.
http://www.ctisoftware.com GOOD LUCK!