The immediate priorities, imho, are (1) building a community, and (2) any stability or installation issues that will allow a majority of users to get going with LinuxMCE. Most of the emails I get are for feature requests. But LinuxMCE already has a gazillion features, and while there certain new features that would be really nice to have, I think the community will be better off if the features that are already there are accessible by everyone.
So, if I was to put the priorities in order, I would say:
1) Find someone who has knows the FOSS world well, has some clout in the FOSS community, and has some free time, and who can act as a community liason to start building a team.
2) Find someone who's good at writing docs, ORG charts and other tools to document LinuxMCE, both enhancing the existing quick start guides, but also laying the foundation for developer docs so that as developers join they can jump in right away. There's actually a ton of info already in the wiki, I think it just needs a clear roadmap.
3) Working with the team to identify the high priority tasks. My personal votes are: A) improving the integration with MythTV. I still get complains that Myth is less stable in LinuxMCE than in stock Ubuntu, which baffles me given that LinuxMCE is stock Ubuntu + stock MythTV. But since the PVR is such a key component, this needs to be resolved. B) Trying to determine what are the installation issues that prevent a lot of users from getting their systems going. C) Implementing the PIN code to protect private media (ie keep the kids from watching Dad's porn
4) The next big, new task will be re-doing the UI to make it easily re-skinnable and themable and improving the designer stuff. This way the creative design guys can work on making it look really beautiful, since the aesthetics seems to be the first thing people pay attention to.