It has great features, and an easy to use, intuitive interface. You can:
- Create tasks on the fly
- Track time against a task, or add time manually
- Create multiple profiles for tracking various tasks
- Move time entries between tasks (in case you forgot to switch tasks while tracking)
- Move tasks between profiles
- Delete time entries
- Export to XML
One nice optional feature, if anyone uses the Pomodoro Technique, is receiving a reminder every so many minutes to take a break. Another optional reminder for the workaholics, aptly called the 'Work-a-holic Deterrent', is one which reminds you that you've been working more than a set amount of hours and minutes.
One thing that bugs me is by default the icons 'flash' on each tick when timing a task (the play button and the icon in the Windows system tray), but it has settings to turn this off. That's what I love about it most, you're not tied down to using it the way they intended, but can configure quite a lot to fit your work flow.
Start using it now!
If there's any other time tracking tools you've found and like, post them in a comment (with a link). I don't think there's any out there now though that are as feature rich and intuitive as Grindstone.