I don't want to spoil your sale but all domainers know that having any Google mistypes and even more the plain trademarked name of Google at the domain name add $0 value to the name. As drazKo said Google can take it back any time You can't prove "fair usage" and the only thing that can do is to drop the name if you get the C&D letter Estibot appraise based on popularity and other factors, it doesn't consult you regarding TMs My suggestion is to drop it or leave it like this, the only reason you didn't get a letter from big G is that it's not popular Just a quick reference for you to read : http://domains.adrforum.com/domains/decisions/466022.htm
Thanks everyone for input. I have not read link provided above, will do it for sure. I guess there are a lot of TM issues out there, Google just is a loud one of course.