I had to go digging to find a good Excalibur thread.
I agree with many of the last posts that this is one of the best King Arthur movies, but it's mostly for those that have studied the official legend (le Morte d'Arthur). The King Arthur legends compile a lot of different stories from both English and French traditions and are not assembled into an easy, linear narrative. They are a bunch of stories cobbled together. It's tough to whittle them down to a 2 hour movie.
As to the transfer itself, the video does not appear to be a bad transfer to me, but draws negative marks from people due the low light film technology of the day. In the early 1980s low light equaled film grain. In contrast, some of the daylight outdoor scenes are razor sharp.
What surprised me, and this probably speaks more to the budget Boorman was working on, was the "canned" sound of the soundtrack, including all of the Carmina Burana portions. It's amazing what we put up with for sound back then (I actually saw this in the theater, BTW).
I cannot speak as someone that has truly heard the Dolby Digital Plus soundtrack (the main track on this disk, no DTS core here). I have an HD-A2 player and a Yamaha HTR-5280 receiver that can do DTS. I have them connected through optical (toslink). For most of my HD DVDs that has sounded wonderful. For Excalibur, however, the downmix to DTS and sent over toslink appears to have some issues on my system (and may for others doing DTS downmix over toslink). Particularly in some of the battle scenes at the end, only the center channel seemed to work well and other sounds simply vanished. My results were much better when I reconfigured my HD-A2 to just send the sound as PCM. That only resulted in stereo ProLogic sound, but it actually sounded better on my system. Yes, it is a little bit of hassle to enter setup to do this, but it's no great loss to me since the original movie was probably only in stereo.