Upgraded 2.3.4-p1 to 2.4.0 With No Issue (Clean Install)
Just wanted to throw out a data point that in my specific setup, I upgraded my [home] Production rig with no hiccups. :)
1. I run pfSense on an SSD and have key material like passwords and my PKI root certificate private keys, so I wanted to play with doing an ATA Secure Erase to properly "wipe" the SSD. I paid $11 for Parted Magic and burned an ISO to CD-R.
2. ATA Secure Erase was successful.
3. Used Win32DiskImager to copy the 2.4.0-RELEASE Memstick image to a USB flash drive.
4. Booted off flash drive. Installed to SSD in about 5-10 minutes.
5. I tried following the Automatically Restore During Install procedure and had a second USB flash drive with \conf\config.xml on it, but it was an encrypted XML file so it didn't work. It's worked in the past with a plaintext config.xml file.
6. Rebooted and manually configured WAN/LAN interfaces from the console.
7. Went to a laptop and used the WebGUI to Restore from an encrypted backup file. It automatically rebooted and started downloading packages.
8. Manually rebooted one more time since I had had issues in the past with FreeRADIUS package not loading until another reboot after an upgrade.
I did run into the gigantic "pfSense" logo but a quick F5 got rid of that. Long story short, no issues with DNS, DHCP, OpenVPN client tunnels, CPU and RAM utilization. Everything seems just like 2.3.4-p1.