Gareth,
I‘m running since two weeks an 4600 gateway with 4GB RAM.
We switched from standalone to distributed and I did no upgrade, we did a fresh install.
Everything looks fine at the moment. We have enabled Firewall, VPN, MOB, URLF, APPCL, ASPAM, AVIR, IPS.
There are only 100 Users behind and fully controlled connections are only at 50MBit/s. Some 1GBit/s connections are working but they are only controlled by firewall blade.
For the way back to the old environment we did some test with snapshots to reverting back. This was the problematic part in the upgrade. We need 1,5hours for a full revert, copying old snapshot to the appliance 20min, reverting from snapshot 1h10min.
Wolfgang