Exactly. You still have exactly the same signal strength in your office, it's just that iOS 4.0.1 is changing how many bars it uses to represent that signal strength on your display screen.
Look at it this way. If I give you a tape measure that is "fixed" so that it shows lengths as longer than they really were and you measure yourself and find out that you're 6 foot 4 inches tall. Someone now gives you a correct tape measure and you now find that you're 5 feet 10 inches tall. Have you just shrunk 6 inches and will going back to your old tape measure magically make you taller again? No, it's just that you've been mislead for all the time that you were using the old tape measure.
- Julian