Agreed, if you go on a run without the iPhone, you will miss the geographical data but, and especially if you did the procedure for calibrating your watch, normally, it should count the steps and so on...
As for myself, I agree fully with Pwalker8 and my experience is mostly the same.
I would just add that I was a Fitbit Flex user and found it a real pain in the a** for recharging its battery. Furthermore, Fitbit is now trying to "go it alone" as far as sharing its data was concerned. Since I have the Apple Watch, the Fitbit Flex is now gathering dust... The watch is a bit different in the health aspect but much more capable!
The watch is part of my health setup which also comprises a Withing balance board and tensiometer, and the MyFitnessPal app. Ever since I started using that kind of systems to truly monitor what I am doing instead of "rough-guessing" it, I shed about 15kg in some 18months (obviously not ONLY with the Apple Watch !
).
So for me, this a trend that will grow...
Right now the watch is far from being indispensable, but like the iPhone 3G compared to its competitors of the time, it is a big step toward something new...
The other app that I use on the watch are Passbook, Navigon and Cyclemeter...