Just flashed it myself. Worked fine right out of the gate. Adds a good bit of snappiness to everything. One complaint - my Cingular MediaWorks settings were not included this time, only 'Cingular Internet' which did not work. Manually set up the connection and I am good to go.
Mine flashed OK. There is an upgraded flasher tool too, and if you didn't install it that might have been the problem.
While on the OS upgrade subject: now that I've lost all the apps I'd installed, it occurs to ask whether there is any way for Nokia to install the upgrade without nuking your apps?
I think this time I'll try making a shell script that I can manually insert all the installs and tweaks I make and then just run that after the next OS install. Linux people: is there a better way?
Since libraries and config scripts may change doing a filesystem diff would be a bad idea in this case.
Your best bet is like you say to write a simple shell script to dpkg install your list of apps, and then copy your other settings and files to where needed.
Did anyone else notice this but it seems to me, that memory handling is a lot better. Some web sites, where previous firmware version reported memory low problems are now browsable. 770 still alerts "Memory low" when pushing it too far, but most importantly it doesn't go to extremely sluggish mode, when encountering a low memory situation, it just reports "Not enough memory".
BTW, that reminds me : Nokia, please notice: 770 is excellent device but the successor of 770 should have a bit or byte more memory.