I think hwat you have suggested below is the safest bet… but remember there is more than one Google user agent too, see here for a start:
http://www.user-agents.org/- you can trawl thru manually, or use the search in top right of the site (obviously search for the word google) – THis search may not get em all tho! – there is an xml sheet in the top left, you can download and sort in excel maybe 
Remember that if you use adsense, you should be especially careful when playing with user agents.
Also read here: AdSense Spider Cross-Pollinates for Google : Natural Search Blog
and a list of robots shown here can be usefull at times: The Web Robots Pages
@HenrikG 216740 wrote:
Thanks for the input, after looking into the different solutions suggested from you and other affiliates and AM’s it has been decided that we will go with a solution that includes using the user-agent to see if it is a bot or not.
So hopefully the stats will be even better, with a more accurate hit stats within a weeks time.
Cheers
Henrik