there's one thing about the 800 that i really liked vs most other, automatic custom wheel size. I dont have to measure the wheel and stuff. if the air pressure is low, it will make almost every other speedometer inaccurate. but with the 800, it will automatically detect the wheel circumference. eg, on my slicks it's 1934cm, with my rocketron mtb tires, it's 2068cm@ 55psi. if i drop the 45psi, garmin will register as 2065cm.

I just check out.. there IS a stopwatch function.. and there's also calories function as well. I got my 800 almost 6 months ago and i'm still learning new functions.
what i really liked about the 800 is cadence alarm and heartbeat alarm. useful for endurance rides so that i know how much to dial back to conserve energy. I'm usually at around 70-75 cadence. and if i realized if my heartbeat is still quite high and my speed is ~25km/h. then i know that fatigue is setting in and/or i'm running out of energy and need more food soon.