Google Search Volume estimate - can it be trusted?

When adding new keywords in the quick add section of the adgroup, does everyone just take with a pinch of salt googles search volume estimate or is it actually reliable? The estimated ad position is pure fantasy but just wondering whether the SV is better as google don't have to put any figures on it?

If the search volume estimate bar was empty, would you bother with that search phrase or could it be a new niche?

Actually having a search volume figure would be superb! Any ideas how to get this apart from the pretty naff overture program?

Thanks

 

Techincally, it should be valid since Google should have actual stats on what these numbers are...but I don't know how accurate it is. It is probably best to do some testing to find out how accurate it really is.

 

It's a total GUESS-timator. Totally unreliable and use it if you want to waste your time.

 

So the search volume bar can't even be relied upon to be vaguely accurate then you think PPC-Coach? Makes me wonder why they bother having it!