It is possible to use videos downloaded by Miro in LinuxMCE already. You simply need to "fix" the permissions on the LinuxMCE videos folder (/home/public/videos/) and perhaps create a miro folder in there, then in the Miro options (on your Kubuntu desktop) point Miro to download to that folder (if you don't fix the permissions it won't let you change to that folder for saving). Once you do that, start downloading some videos and they'll show up in the Videos section of LinuxMCE shortly. The one downside (and a reason for more tightly integrating it) is that some shows don't use a nice file naming convention, they assume you'll be using the RSS for your metadata and so when looking in LinuxMCE all you'll see is some obscure filename. Thankfully many publishers are slightly smarter than that.
Thanks a lot for this very useful information. It is indeed a good starting point. I hope that tighter integration will nevertheless come at some point.
Do you know whether we can do something similar with podcasts using itunes from a winPC or any other application in linux?