I think one of the factors making the DM2 shots look bad is the unnatural approach id took to lighting back then, using multiple lights to represent light from the sky as this screenshot taken at Scampie's location 3 indicates -
http://puu.sh/hVGCZ/4ed3224645.jpg (taken with DarkPlaces and r_editlights 1 for the sake of convenience).
As a result, you get shadows being cast in several different directions, in a location where one sees a sky above and no other light source and thus expects all shadows to be cast in the same direction. Consequently it ends up looking weird when they aren't. This wasn't quite so prominent with lower lightmap resolution.
I think of all the screenshots Scampie took, the one at location 4 looks best, and that's not surprising since there is only a single light source there -
http://puu.sh/hVH6K/089cd1541c.jpg - and thus it looks more realistic. However, as others have said, even in location 4 there is the issue of the shadows looking unnaturally sharp a la Doom 3 and the increased resolution can produce that old problem of better quality media appearing dissonant with the low fidelity of most of the game.
Nonetheless, ericw, I think once people have worked out what combination of compile options works best for a given scenario, this will be a really nice feature and I wouldn't be discouraged by the mixed results so far.