In the process of searching for the HC-SR04 in the forum, this thread has popped up as the most useful resource. I've downloaded the library and run the demo code which works just fine unmodified. One strange aspect is that when it's uploaded to my Uno (1.0), the first measurement appears valid, while all others run to zero. If I press the reset button, all is good until next code upload.
Should I jump to the newer version for my device and if so, what complications can I expect?