For my future reference if nothing else, based purely on watching Shingu on DVD:

Xine on Fedora 8 has much better handling of DVDs than even a bleeding edge mplayer, but mplayer has better deinterlacing and keyboard controls for pausing and so on so I used mplayer. Mplayer did turn the subtitles to mush in a few places so I went back and re-read them with xine. More modern versions of Xine may have better deinterlacing, which would probably make it almost completely superior.

Different players have somewhat different renditions of subtitles. My Xine shows them as solid yellow text; mplayer shows them as semi-transparent white text. Most of the time I prefer mplayer's style, at least when it's not garbling the subtitles.

(The Fedora 8 xine also has the irritating habit of leveling the left and right audio channels when it starts. I deliberately have mine slightly off balance because that's what it takes to sound right in my setup.)

Mplayer usage: gmplayer -nocache -vf yadif dvd://N, where N is the episode/title on disk; at least for Shingu, yadif was the best option for deinterlacing out of the ones that my old computer could do in real time. Occasionally I needed '-aid ID' as well to make mplayer use the Japanese audio track (by default I believe mplayer picks the first audio track; on most of the Shingu DVDs this was Japanese, but on one it was English). You want to stop and start gmplayer to change between titles or otherwise change parameters; when I did it from the gmplayer menus, the very bottom bit of the picture got this shifting green cast. I could not get mplayer's DVD menu support to work at all well, so I did not attempt to use it.

(I suspect that live action may call for quite different deinterlacing options than anime.)

I admit that it was periodically tempting to give in and download a fansub for Shingu, despite having the DVDs. I suspect I would have had somewhat better visual quality (since someone who knew what they were doing would have deinterlaced it well) and a better rendition of the subtitles.

(As I mentioned in my reactions, modern softsubs are clearly better than DVD subtitles. This should be unsurprising; among other things, modern subtitles are higher resolution.)

PS: the sign that one's anime DVD needs deinterlacing is that things moving sideways get this comb effect at the edges, as half the pixel lines are displaced relative to the other half. It's very visible.

PPS: if people have opinions on the best Linux DVD player for anime and the best settings for this, I'd love to hear them. I can't say I've done extensive experiments here.