We started using AxoSoft OnTime 2007 for development / defect / support incident tracking last week, and so far it is working out great. We researched and tweaked the application for many hours before making the decision to switch from Ready Desk for the support ticket management.
The application is very easy to use and quite configurable. I believe the Customer Portal section used for the support incident tracking is brand new in the recently released 2007 version, so we look forward to a lot of improvements and growth of that area. There are a few week points, such as email management and CRM, but so far we've worked around these issues.
Overall it is a great product and I know that it will give us a much better view of our development tasks and schedule than we had before. After a few more weeks with the app, I'll write a follow-up.