YES!

I have to say that with my Irvine .40, I ran at least a gallon before it was making good power, and to be brutally honest it vibrated A LOT.
However, after most of the summer (1997) in a Sig Kobra, it started to calm down.
Now that it has seen duty in a couple of planes, and has a good amount of time on it, it is SMOOOOOTH, and starts and runs like a dream. If it ever wears out I will buy another in a heartbeat.
Another engine that was very similar in it's breakin was my Enya .40- not real good power, and vibrated a lot. It finally was running good, so I let one of my buddies put it in his Global China clipper, and he buried it 7" down in the hard August Ohio dirt. Nothing broke, but it vibrated so bad after that I made him buy it!

Jetts