I have seen some changes in Google's Adwords Keyword Tool. I have done Keyword research and received a set of results, but when I do the research for those same keywords a few hours later it returns completely different results.
Is there a free keyword tool out there that generates reliable results?
All tools work with incomplete data (or show you incomplete results). This problem gets worse the further you are away from the US, as you often don't know if the results come from a particular country or time of the year.