Jim,
I have not used heading hold for takeoffs because I've only used the gyro for 3D. However, if you go to the Jet forums you will find many jet pilots use HH gyros for takeoffs to keep their aircraft from getting away from them. Below is an excerpt from Futaba's web site:
http://www.futabarc.com/faq/faq-gyros.html#q340
Lastly, gyros are extremely popular on the rudder of scale aircraft, especially complex nostalgic aircraft which are notorious for difficult ground handling. In this case many modelers DO use a heading lock gyro or AVCS (heading hold) mode in a switchable gyro, but then turn off the heading lock feature the moment the model breaks ground. This way the model will literally track perfectly straight with no rudder input from the pilot whatsoever.
I'll try my Twist, a tail dragger, in HH mode for takeoffs and will let you know. Remember, if it is set up properly and you have the gain set wrong the tail may wag. Again, if you can always turn the gyro off by flipping a switch and then lower the gain before the next takeoff.
Hank