I'm re-reading this thread and some of my contributions, which I feel are unclear. So...
Many, if not most, or even close to all TMS/LMS systems at theaters are Windows-based. Many of these do not have the capability to read Ext2/3 out-of-the-box (I think Hollywood Software's TCC3 does, and probably Arts Alliance). This is the reason that the labs (Fotokem, Deluxe, Technicolor, etc.) send movie trailers out on thumb drives formatted NTFS, not Ext2/3. Think about this: they get the same 4GB or 8GB drives we do from the store or wherever, which are FAT32 when you buy them. They go to all of the trouble of re-formatting these drives, but NOT to Ext2/3. They go with NTFS... Why?
This has nothing to do with DCI specs, but rather with the theater/library management software. I'd be shocked to find out if there are any DCI requirements for TMS systems; they just have to be on the media and/or management network and they can do what they like. At most multiplexes the TMS/LMS is the main point of contact with the servers. Whatever you're producing will most likely be ingested from there. Make your drives NTFS-friendly, especially if we're talking about ads, trailers, shorts, etc.
With features I think it's a more fair point to make that Ext3 is the way to go. But then, the theater staff deal with features differently, too. Trailers they want to ingest and schedule at one sitting. Features, meanwhile, they plug in to ingest and then walk away for a few hours, going about their business.