I followed the upgrade instructions on the homepage since I figured that RC2 might not be too different from the final version and everything went smoothly but using apt installed some level 4 and 5 updates (obviously)... I wonder if this will make my system unstable - I don't mean the odd glitch here and there but unstable as in "render unusable".
This is what I did, roughly, and had no problems except as expected (documented bugs, not Mint's fault).
What I'd actually done was a CLI upgrade. I'd previously installed 048 and done some 1/2 updates. Then Sunday I followed the upgrade instructions from CLI with the difference that my sources.list was largely uncommented. Thus, backports and proposed and unstable were all available to me. I was planning that I'd need to do a clean install anyways, so worst case is I waste some bandwidth and brick my 048 install.
No bad karma. Everything went fine. Now running Elyssa with the -19 kernel and everything from proposed. Its like having Elyssa based on 8.04.1 instead of 8.04. The problems with this approach, as pointed out in the docs, are many. I need to go through my system very carefully looking for bugs and cannot blame Mint on anything I find. I noted OpenOffice upgraded to 2.4.1 and at the same time went from green to orange splash. I did lose my desktop background on reboot, put it back in place manually, and it appears to be sticky. I'm running the restricted fglrx for my ATI card but haven't run EnvyNG to install the proprietary ATI driver; nevertheless, Compiz enables fine and suspend/hibernate both work properly. I haven't tested for interference with video playback or with Impress/Powerpoint. In the past I only get dual monitor support on my laptop with proprietary ATI through the Catalyst control panel; I don't expect this has changed.
Flash works perfectly now for me. My kids and I killed 30min last night watching dumb stuff on YouTube with my laptop (Elyssa.proposed). I advise anyone with Flash problems to do this:
apt-get remove --purge flashplugin-nonfree libflashsupport
apt-get install libflashsupport
apt-get install flashplugin-nonfree
That worked for me. Cut-paste those lines from Clem's upgrade instructions. It may have worked so well for me because my sources.list has very few ## lines in it.
My overall initial impression of Elyssa is that it boots to the login faster than Daryna, but Daryna-KDE gets to the desktop faster. Profiling and tweaking writeback should help Elyssa. Tweaking Sessions should help Elyssa. Elyssa is crisper once on the desktop than was Daryna, but not crisper than Daryna-KDE although Elyssa launchs OpenOffice faster than Daryna-KDE (OO 2.4.1 vs OO 2.3, so not direct comparison). FF3 on Elyssa launches slower than FF2 on Daryna-KDE; this may be due to profiling/writeback tweaks. Once I sniff the bugs in my nonstandard install, I'll know if I need to do a clean install. I'm treating this system as "Elyssa.proposed" rather than "Elyssa.stable" due to the -19 kernel and some 3/4/5 level updates, so YMMV and I won't be complaining here when I stub my toe on something.
I don't advise following my upgrade path unless you 1) know what you're doing 2) are prepared to do a clean install 3) have good backups and 4) have another bootable partition as a safety net.