We generally use Impact for ticketing with other ticketing applications like Remedy. We also use it for enrichment of other applications that collect information from different sources, such as on the internet. But primarily, we use Impact for ticketing purposes.
It's a customer-centric product, so in my current company there aren't that many people who use it as an end-user application. In fact, it's mostly only used by the Netcool team, rather than any end-users at all. Only the Netcool/OMNIbus event console and event dashboard will be used by the end-user. In the Netcool team that uses Impact, there are probably 20-30 people, and they assist with the console.