Finally decided to splurge on the box - I've been through the 5.1 three times now and I think you’re right on the money with this. The drums sound balanced to me, but they’re really isolated and often sound--on my system, at least--kind of detached from everything else happening in the other channels.
Working with a (presumably) mono drum track obviously limits your options when mixing for surround, but I’m not crazy about this approach. The effect of having the whole kit locked to that one speaker and beamed right at you is rather distracting at times, particularly on the more active tunes (“Across The Great Divide”, “Rag Mama Rag”). I loved Clearmountain's 5.1 of Big Pink--which basically follows the same mix philosophy, if I recall correctly--so I'm sure why it bugs me here.
To my ears, the mixes that work the best either have very little rhythm section presence (“Whispering Pines”, “Rockin’ Chair”) or he's allowed the drums to diffuse a bit into the front channels. For example, “Up On Cripple Creek” has the kit at a slightly lower level in the front left channel in addition to the center.
Not quite sure how to vote yet as, on the one hand, I respect the bold choice to go crazy and basically hard-pan everything on a classic album - but I also think that it often sounds less cohesive than the original, like you’re just listening to isolated elements positioned around you rather than a fully-realized surround mix. This is probably the only time you’ll hear me say this, but some of the guitar solos in the right rear channel actually seem overloud (!!).