When things run so smoothly I forget it's a good idea to write those who make things work.
Ease of use: Check. One does have to dismiss dialog boxes and enter a administrator password for installation. I don't know if it would even be legal for VT to automate the license acceptance. Otherwise, it's auto pilot.
Support: Check. I've had VT write me several times about installation issues. When I was new to their application I tried to populate the update list by dragging apps from the mounted DMG. Oops.
Features: I like the options of seeing what information shows up in the Watch List. I prefer the short description for instance and I uncheck the OS column. I also like the option of which HD partition to scan.
Quality/Stability: Never crashes. Sometimes slow. Nearly all the apps self-install except for Widgets. I keep utility files and lesser applications scattered over several partitions and VT finds them and installs them.
Price: The annual fee is justified and compensated for in saved hours of monitoring and installing updates manually. Just figure how long this would take you and multiply times your hourly wage. I would say it pays for itself after the first month.

No apologies, I'm an unabashed VT fan and proselytizer.