Well, we've certainly seen microsoft release insanely insecure operating systems in the past while swearing up and down that they were the most secure thing on the block.
So we certainly can't just assume "Oh, it's microsoft, so of course their product is secure", but at the same time, we can't assume "Oh, someone said they hacked windows 17 ways. Windows is totally insecure."
I would say since you're dealing with information security it's better to err on the safe side, but it's also better to err on the not-giving-people-money-unless-they-can-back-up-their-big-talk side.