Whoops, one more note, there was a caution about the lcd and interrupts at:
http://www.arduino.cc/cgi-bin/yabb2/...m=1173553276/3
it is summarized as follows:
1.) Never use a delay or any library which introduces a delay while in an interrupt (like the Wire library or LCD libraries). Serial communication, or any communication requiring a clock will also fail.
2.) Use an external pull-up on the interrupt line.
re: 1. not a problem if updateDisplay is called directly in loop() as I'm suggesting.
re: 2. This is an external hookup issue.
Also I did some scratching and I think worst case scenario (i.e. a v8 with tbi doing 150mph at 8000RPM), there should be about 10 milliseconds of overhead for all the interrupts, which leaves .99 seconds to figure out what to display and display it.
P.S the 2x16 showed up today, I still can't tell if it is the one with less built in characters but more user definable characters or not.