Hi Nick
First of all - nice and simple class.
One thing that seems to trip up beginners to the Arduino is the idea of implementing delays without using delay().
I think one of the main issues with going from blink with delay() to blink without delay() is that the mindset of the beginner has to be changed.
Blink with delay():
You turn on the light, you waite, you turn off the light, you waite. The loop() executes once. Plain simple and most beginners get it fast.
Blink without delay():
Change of mindset - the loop() executes alot of times every second and we do not want the light to go on/off each time it loops. Turning light on/off is done by comparing time.
I think a destinction beween the two should be made verry clear in the preface to the Blink without delay() example.
Comments to your class:
How about a functional overview in the header:
// reset(); Reset time
// intervalMs(); Return numbers of milliseconds since last reset
// intervalUs(); Return the numbers of microseconds since last reset
I think the example is a bit too complex for a beginner. I would have made one with with Serial.println, one every second and one every 1.3 sec. The beginner does not need to fittle with diodes and recistors to see the example working.
Jyst my two cent.
-Fletcher