I still miss the 770 cover, but as the next devices changed to an always-connected philosophy there was no need for the magnetic switch and I can see (though not entirely agree) why they removed the whole thing.

Other than that, the N800 trumps the 770 in every way (faster CPU, double the RAM & flash, more storage expansion, stereo speakers, webcam, FM receiver, stand and so on and so forth). Case-wise, I found the "official" N800 case (SU31) an adequate substitute, but then the N810 came and the keyboard (such as it is) trumps everything else for me (still looking for a good case for that).

With 64MB RAM, OS2006 is still the best option (as long as the wifi driver RAM corruption bug is patched, otherwise you risk spontaneous reboots, loss of data etc).

Fast booting isn't such a priority IMHO (current uptime: 46 days, and only because I was asked to switch it off by an overzealous flight attendant).