Many people have reported that after updating their software for their airport cards to version 3.4 their signal strength has dropped. I noticed the same, so I ran some tests. Signal strength has not actually dropped, but the gauge showing how many bars of quality has. So this brings up two real possibilities. Either there is a bug in the software in the calculation of how many bars should be displayed, or the calculation of how many bars should be displayed has simply changed. Either way the signal strength has not changed. If anything, it has improved due to some software tweaking on Apple's part. So don't panic.