I use my turbo timer more for warming up purposes than anything, because 95% of my driving is within 5kms of my house (work, gf, uni) so without it the car would never get to ideal operating temperature..
Was the worst install in my WRX though
Getting around the factory alarm, keyless entry system and the key detection security function = flat battery and many trips to J Car
My VR4 came with one, I used it to warm up my car in the mornings haha.. Switched it on, and locked up the car! If you tried to drive with the turbo timer the steering would lock, and the car would switch itself off.. I tried it, just to test it haha..
When I got my alarm fitted shortly later it came with an inbuilt turbo timer which ran for a minute after switching off the ignition.. I had to either stall the car, or press and hold the alarm button to deactivate it!
Warming up purposes makes it worth it for me..
That and the random good samaritan at the shopping center chasing me down to tell me my car is still running