Apps that track your routes tend to be battery-killers (not really their fault, more due to the way the SDK insists they work). The ones that create exercise playlists depend on time-exhausting Mac-based solutions that have to analyze your iTunes tracks for their beats-per-minutes, creating a heavy investment with a minimal payoff. Genius on the iPhone does a decent job, without that time commitment.
I don't quite get the food and exercise logging apps -- I find that it's simpler to do all that on my primary Mac, using a physical notebook (you know: paper, pen, old tech) when I'm on the go. As for the stretching and exercise guides, I find them awkward. I'd rather use a DVD or a Wii-based game (I adore Gold Gym's Cardio Boxing, for example) where I don't have to keep referring to a 4-inch screen all the time and the sound is clear, and the instructions are easier to follow.
So what am I missing here? What are the really good iPhone-based fitness apps? I feel like all the ones I've tried just keep missing the point: to make exercise better or funner(™ Apple). Yes, they make exercise more portable, but do they provide a better win over Nike+, a bike computer or a garmin?
Please do chime in in the comments. Let me know what iPhone Apps I have been missing, and which ones will improve my exercise experience, whether in the home or on the jogging path. Surely, there have to be some winners out there, and I'd love to hear about which apps are working for you, and why.