I did some testing, I have an airport and airport express. I also have a 17 inch powerbook, I brought it inand litteraly touched the airport with my laptop, and the bars stayed at 2, but i used a program and checked the strength and it was at 81, i walked away 10 feet and it stayed at about 68-72 signal. The bars stayed the same. Now since the 10.4.1 upgrade, the bars are more true, but using Istumbler as suggested the signal was more or less the same.

On another note I have noticed people stating they cannot get an address or that they are losing connection. I have had a similar issue, where the service lookupd reports a hangup and restarts, when this happens as report in my system.log I must shut off my airport card and turn it back on, no idea what is causing the hangup, since the 10.4.1 upgrade it happens less frequently but it still occurs. I am going to try the shortening of the computer name as it is a bit long at the moment DevilMayCryForMe....i will shorten it to DMC and see if that fixes the issue. Below is a bit of the system log that is reporting the error.

/var/log root# tail system.log
May 18 08:31:59 DevilMayCryForme configd[34]: posting notification com.apple.sys
tem.config.network_change
May 18 08:31:59 DevilMayCryForme lookupd[22545]: lookupd (version 365) starting
- Wed May 18 08:31:59 2005
May 18 08:32:08 DevilMayCryForme kernel[0]: AirPort: Link UP: "Base Station" -
00112404ec4d - chan 11
May 18 08:32:10 DevilMayCryForme launchd: Server 0 in bootstrap 1103 uid 0: "/us
r/sbin/lookupd"[22545]: exited abnormally: Hangup
May 18 08:32:10 DevilMayCryForme lookupd[22638]: lookupd (version 365) starting
- Wed May 18 08:32:10 2005
May 18 08:32:10 DevilMayCryForme configd[34]: posting notification com.apple.sys
tem.config.network_change
May 18 08:32:10 DevilMayCryForme launchd: Server 147a7 in bootstrap 1103 uid 0:
"/usr/sbin/lookupd"[22638]: exited abnormally: Hangup
May 18 08:32:10 DevilMayCryForme lookupd[22639]: lookupd (version 365) starting
- Wed May 18 08:32:10 2005
May 18 08:32:12 DevilMayCryForme mDNSResponder: Repeated transitions for interfa
ce en1 (10.0.1.2); delaying packets by 5 seconds
DevilMayCryForme:/var/log root#