I posted something similar to this on the JRMC forums, but I'll post a more generic version here.
I came across this tread because (after seeing a good price on the M1001 in an add last week) I've had renewed interest in DMRs. Some useless background:
I use SageTV for all my video needs, it streams recordings, DVDs, etc to my two TVs (HTPC driving my HT system and MVP/Extender driving my "normal" HDTV). I love it, can't imagine living without it.
Similarly for music, I run J River Media Center, I have it's Media Server running on my server and I use JRMC "clients" on my HTPC, desktop, and stream music to work (on the fly transcoding is sweet!). For a long time I thought I wanted JRMC integrated into SageTV (my two favorite media apps in one, what could be better). But after actually thinking about how I listen to music and such, I came to the realization that I use them very differently, if I've got a TV on, I'm watching video of some sort (not music). And if I'm listenning to music, I don't have a TV on (thus no way to browse music via Sage or a Sage-like interface).
What I really need is a DMR or two (or three). Something I can just have hooked up to speakers so I can listen to music either in places without a TV, or without the TV/display on.
OK, useless background out of the way, I need to pick a DMR. Like I said, I love JRMC and am completely addicted to it's smartlist feature. For those who don't know, Smartlists appear in JRMC just like a normal playlist, however unlike normal playlists, with a static list of tracks, you define a Smartlist by criteria (eg Genre, Rating, last played, etc, etc). Then when you select a Smartlist, JRMC automatically generates a playlist based on the Smartlist's criteria.
While I don't have a huge collection, I don't like having to pick individual tracks (though I like the ability to), nor do I like picking playlists, 99% of the time, I use the Smartlist. I've got them setup for my favorite genres, stuff I haven't heard in a long time, etc.
That brings me to my requirements for a DMR:
1) Needs to integrate with JRMC: JRMC supports UPnP serving, and presents smartlists to the UPnP client.
2) Needs to support lossless audio: My entire collection is lossless, WMAL at the moment, but I'm not married to it. Unfortunately JRMC can't transcode to PCM/WAV so I need a DMR that supports lossless codecs (other than WAV) natively.
3) I'd also like an alarm function, so that I can use it as an alarm clock radio.
FWIW, I really don't like the Slimserver/player interface, or more correctly, it appears to have nothing like Smartlists, and I just can't live without something like that. Maybe I'm missing something though.