I have looked at probably 35 to 40 and maybe even 50 lap timers on the App Store, both paid and nonpaid, and Lap Timer is the best design by far.
In order to time laps, you have to be able to mark a lap without even thinking about it.
The lap button here is so big that you can't miss, while other similar apps have lap buttons so small that you constantly miss marking the lap, or you have to look away from what you're timing to make sure the lap is marked that you can easily lose your place in the event you're timing.
A similar app actually places an ad right up against the tiny lap button so users wind up hitting the ad button half the time. What were they thinking?
Not much. Not like these guys at RandomVisual.
Five stars for the app and five stars for the developer. Both are exceptional.