I came to LMCE as a user of knoppmyth for many years. LinuxMCE by default loads a backend on the core as well as the Media Directors. It is automatically configured to utilize systems (MD's) for many things including delegating the commflagg-ing bits to any not-in-use MD's. As deployed the system or core or core/hybrid is the default master backend, and this is where all the recordings are stored. You can have tuner cards in any or all of your MD's, and they automatically write their recordings to the core. The core will have a default /home/public/data/videos/tv_shows_1 for itself, as well as an additional tv_shows_<moon number> for each of your media directors.
In my current configuration, I have the core/hybrid with two pvr150 cards capturing recordings/LiveTV from my 2 satellite receivers (Dish Network), on the ManCave MD, I have 2 HDTV-OTA cards for capturing HD free to air content. I also have 3 more MD's that can either view/schedule recordings from any or all tuners, and this is consistant across the board for any of the MD's.
The MD's themselves all run a backend, and therefore if you are commflagging or running any other mythtv related jobs (ipod, portable, commercial removal) The Core will look to see which MD is being utilized the least, and send the jobs there for running, so as not to bog down the MD that is being utilized the most. So in theory all of your traditional slave backend are automagically configured and set up by the core, as well as the centralized storage location, being shared to all connected MD's.
So to sum up. Make a back up of your existing Mythconverg DB, and migrate your recording storage over to where your core - core/hybrid will be located. I still have my knoppmyth recordings, or at least a few that I did not want to delete, or re-record, and I imported the old database into the new one created by LMCE, so you don't even have to lose your recordings, if you so desire. I have wiki'd the base steps for this here:http://wiki.linuxmce.org/index.php/Mythtv:RestoreRecordingsAfterUpgrade
as well as my remove commercial settings here:http://wiki.linuxmce.org/index.php/Mythtv:Remove_Commercials
So if that helps any, good deal.
I think you will find that LinuxMCE will do everything you are used to, as well as some new things, in my opinion, you will wonder how you ever lived without!