I've used this product for 8 years. I find Managing Test Life Cycle and Reporting to be the most valuable components.
Test Management has become very easy. All the test cases are tracked and reports can be run on various factors to decide productivity, code status, defect density etc.
Integration with an Agile Tool (e.g. RTC)
It's straightforward but sometimes it can interfere with other products because of lots of client components.
It's a very strong product which comes up with lots of additional add-ins.