Ticketing: email reply works but creation in the UI is a pain. You need to click 3 times after logon. Quickadd also 3 clicks.
Dashboard: can't configure to show your project logs. So for large companies with many projects the dashboard is useless
Gantt chart: that's a 3rd party plugin in flash. Can't handle dependencies. Can't enlarge timelines, ticket changes don't get reflected here and changes here don't get reflected in tickets.
iCalendar feed: nice
UI: my general impression is that it is overcrowded
People: adding people is a pain in a large company, no search facility here.
Time tracking: nice
Summarizing: there are free solutions out there with much better usability