I got a Tinytach as well. Super-simple install, too bad it doesn't have a backlight... Worth the $65 though.
I mostly use it to verify my speed because my speedo reads waaay low. The tach helps me keep around 3250rpm on the highway (around 60, and plenty of RPM anyways) other than that I have only used it to check and set idle speed and max governing speed.

I have to agree with iNeon though - not a great need for a tach on these cars, but I found that out after installing the tach If I ever fix the speedo, the tinytach might be removed. I think removing the clock for a tach would be a disservice.

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1971 220D/4-speed ~250K mi. Family owned (dads side) through three generations since <5K miles.
1992 Chrysler LeBaron, 3.0V6 125K. Family owned (moms side) through three generations since new.
1977 Chevy Camaro Continual hotrod project
1970 Cadillac Sedan DeVille 472ci and nearly 19' long
1974 Fiat Spider Still needs work