Just an add on to the previous post:

"ISTJs are easily frustrated by the inconsistencies of others, especially when the second parties don't keep their commitments. But they usually keep their feelings to themselves unless they are asked. And when asked, they don't mince words. Truth wins out over tact."

http://typelogic.com/istj.html

Started laughing when I read that. Sheepishly admitting i'm guilty of that! :)