My current install is 1004. It started out as a very early 810 alpha, and was apt-get upgrade'd throughout.
apt-get upgradeing is possible, but there are quite a few pitfalls, NONE of them related to LinuxMCE, but only related to Ubuntu packages. Mainly packages like flash installer and the sun java stuff. If anyone is inclined to spend some time on repeatedly trying to apt-get upgrade an 810 to a 1004, and document every step that's needed, up to the point where in the end we can create a small script which will help people do the upgrade, just do it. Work like that is always highly appreciated.