Just looked their site again, it is called Verticle now (used to be called artisoft). The price is higher now, but it supports VOIP and IP phones.
I like Norstar system that no fan, generating little heat, low failure rate on components, capability to do sophiscated routing rules. But I also like Televangtage easy to use for both administrator and end user, rich in features.
The feature I missed most in Norstar compares to Televantage is lacking the ability to have remote user transfer the call using the phone system features. Since Norstar already through ATA support those escape sequence, it can easily replace the "flash" with "**" allowing remote user using the phone system features. I don't know why they do not add that feature to fit the trend that many companies allowing people working remotely these days.