I installed mer 0.12 on my n810 last night and I have to say it's very impressive but not ready for day-to-day use.

I really like the layout that maximizes screen real estate and the inclusion of the jaunty repos is a nice touch.

I did have a few issues/suggestions:

1. The application manager dialogs didn't seem to have any way to close them
2. The vitural keyboard appeared for all text boxes. A tool to turn it off would be nice since n810 doesn't need it.
3. A tool to add items to the mer menu would be very nice. Even if it's just a cli app that takes a .desktop file and category as arguments and generates a menu entry it would be great since currently you have to launch jaunty software from xterm
4. The font size used for the mer and applications is very small. If it were larger finger usage would be a lot easier.
5. On behalf of lefties everywhere a left-handed version of the default theme would be much appreciated. The scroll bars on the left hand side goes a long way towards making the device much less frustrating

mer isn't quite ready to replace maemo but once tear and a few more hildonized apps like pidgin are ported it will certainly be close