EDIT: The problem regarding recorded shows being lost has been resolved. My silly mistake.

I just upgraded from R5A16 to R5A30.2. Here is a summary of how things went. As much for the devs as anybody

In general it went very well. I was really amazed to see how much things have changed. I the install & setup really (attempts) to do a lot of the work for you!

I had an initial problem,
http://mysettopbox.tv/phpBB2/viewtopic.php?t=7894&,
where after the upgrade, the system would mysteriously boot the previous kernel, and not finding any of the appropriate kernel modules, was extremely borked. I discovered there was some bios wackiness surrounding a secondary disk and my dvd drive. after detaching the secondary disk and finally clearing the cmos, I re-attempted the upgrade--and the problem went away.

After the install, I noticed that the initial boot process was attempting to automate configuration of a bunch of stuff including downloading nvidia drivers--Very impressive!
Unfortunately networking wasn't able to successfully lease an ip address via dhcp, so the nvidia install failed, and as a result gdm failed as well, leaving me at a login prompt. I logged in and took a look around. ifconfig revealed that their was, in fact, an eth0, so at least the hardware had been detected, and appropriate kernel module loaded. It didn't have an IP address though. I tried to ifdown and ifup the interface, but the ifup/down scripts didn't recognize eth0. So, instead, I ran dhclient, and it leased an address. I rebooted to see if this would resolve itself after the initial boot, and it did.

Nvidia drivers were installed automagically and gdm started.
I answered questions as they were presented (again, very slick!). Had to look inside the battery cover of my hauppauge silver remote, to confirm the model number.

Everything seemed to go fine until I saw output along the lines of "creating/testing images". When it got to 3 of 5, the system locked up hard. No mouse, no keyboard, no virtual consoles, no pinging from outside. Not knowing what else to do, I hit reset. I was pleased to see the initial configuration restarted itself. Again when it got to 3 of 5, it locked up. I reset again, and this time I opened a second xterm before proceeding and ran top.

When it got to the "creating/testing images" part, I noticed that "convert" floated to the top. This time it made it all the way through without locking up.

Finally the initial setup finished.

I think the thing was that the frontend couldn't run because it was missing a theme I had been using, MythMediaCenter. Fortunately, from previous experience, I knew to make backups of any non-standard themes. I copied that theme, along with my OSD theme back into place. I ran mythtv-setup, and I noticed that many settings had been preserved, but not all. When I set up my tuner card (PVR-250 w/directv), I realized I needed to copy my rca.pl script back to /usr/local/bin. Since this had to be highly customized to work with my directv reciever, it's a good thing I backed it up. Finished with the setup, I started with the frontend. It kept complaining that all tuners were being used. Nothing in the output or logs provided a clue. So I tried various combinations of deleteing/adding the tuner & tv source and restarting the backend. Finally I got it to work. I never did track this down to a specific problem.

I lost some customization in the frontend setup, such as OSD fonts, etc. But little by little I've been fixing these things.

In order to get my tv out going, I had to restore my XF86Config-4. Since this was a pain to configure initially, I always keep a backup of it. I copied the original to XF86Config-4.orig then dropped my copy in place. Amazingly it just worked.

I have a custom script that enables me to kill & restart the frontend from the remote. Had to restore that to /usr/local/bin.

For some reason my bash profile isn't restored. I just get a generic sh prompt. I'll try restoring .bash_profile and .bashrc.

The only major remaining issue,
http://mysettopbox.tv/phpBB2/viewtopic.php?t=8313
is that somehow it can't find any of my recorded shows, even though they're there. I'm hoping I somehow screwed up the paths in the backend configuration. <fingers crossed>I'll be able to check when I get home</fingers crossed>

So all in all, it was a pretty good experience.
Things that were a royal asspain, previously, that Just Worked(tm) this time.
Installing nvidia drivers (still had to restore my XF86Config-4)
Configuring nvidia-settings: I have a custom script in my home directory that, among other things applies the nvidiasettings rc file. This was restored automatically
Setting up lirc
Lirc configuration--this was restored automatically.
Setting up ivtv
I'm sure there are some other things, but I can't recall at the moment.