So Apple released a nice iOS-looking update to this utility, however, it's lacking all the things the iOS one is also lacking: printers, wireless client/signal strength, logs, SNMP and IPv6 settings...
Existing settings remain, so if you don't need to make changes, you're good to go. Otherwise, they also released AU 5.6, which keeps all the old bells and whistles
Yes, I would say 6.0 is a major step backwards, at least from a functionality standpoint. Can't configure SNMP for monitoring, can't set up any IPv6 stuff, no signal strength, logs. I really hope this is not the direction they are going, but rather just trying to get version 1.0 out the door.
http://support.apple.com/downloads/ has Airport Utility 5.6 as a manual download which has all of the old stuff. Everyone should download it so they see a high number of downloads and know folks want it! ;D
Also out is software 7.6.1, which supposedly has a number of minor bug fixes in it. I'm giving it a try.