Like shoving a personal trainer in your shorts. – iSmoothRun Review

Update: 4ish years later, and this is still 5 stars and still the only running app I use. I wish there was an active fitness level rating similar to the VO2 that the Jabra app gives you. Otherwise, can't think of a thing I'd change! Best running app on the iPhone hands down - cadence coaching, user laps (!!), shoe mileage, Pebble integration (with a full-on custom Pebble app, so you can trigger laps, pause, and show multiple pages of the huge amount of info iSR knows!), weather/fastest song/more recorded each workout, ghost runs, extreme interval editing, great graphing and calendar view, smart switching betw gps and accelerometer when gps coverage drops, uploading to RunKeeper, MapMy, email, and even up/download backups via Dropbox... Awesome sauce. Bottom line: best running app on the iPhone. Period.
Review by tim05401 on iSmoothRun.