The trails up top are perfect for interval work, the hills are perfect for hill work, and the grass is perfect for drills/stretching.
The only reason I didn't give the park a perfect review is because a lot of people who visit the park let their dogs off their leash in the trails thinking no one will be around and my runners get chased and/or stopped mid-run quite often. This is frustrating because Sunnidale Park has a beautiful Dog of Leash Recreation Area (DOLRA) steps away. I understand that most dogs are friendly but even a friendly dog can run between a runner's legs resulting in an injury or at least a scare. There is a dog off leash recreation area (DOLRA) in the valley of the park (very well maintained) with trails.
Not only is the park suitable for all running needs, but it is incredibly beautiful, well kept (yes...even the porta-potties are cleaned), and is an overall great park to connect with nature. The Middle Loop gives runners a great tour of the park.