Well I've just installed Network Guardian 2008 on my backup proxy box so that I can then swap it in with the live one to get NG08 installed on the main rackmount proxy.

So far the upgrade on the spare has been fine it picked up all the settings it needed as part of the installation.

One thing I wasn't successfull with under the last version was active directory integration for authentication but with NG08 it seems to be working fine at the moment.