InsightConnector - A Viable Exchange Alternative?

Fading Captain asks: "I'm sys-admin for a mid-size organization and have returned yet again to that fateful question: is Exchange the only viable groupware server in its class? Unfortunately, browser-based solutions won't cut it in my case; management wants all the bells and whistles offered by Exchange. However, I haven't seen any mention of the InsightConnector product made by a company called Bynari (with whom I have no affiliation). Bynari claims the product will fool MS Outlook clients (full, not Express) into thinking any ACL-enabled IMAP server is an exchange server. In other words, my users can potentially utilize the groupware features of Outlook (which said users are beating down my door to do) while I run an inexpensive Linux mail server behind the scenes. Sounds too good to be true. Anyone subjected this configuration to real life testing?"