poita said:

Without going through the 56 pages of the THX thread, I have the Japanese LD with the all white cover and THX-1138 written in the middle in metallic writing. Is it worth doing, or has it already been done?

Well, since I was the one who asked, I took up The 56-Page Challenge. :)

... six hours later ...

http://originaltrilogy.com/forum/topic.cfm/THX-1138-preservations-Italian-Cut-available-see-1st-post/post/478709/#TopicPost478709
On page 20, msycamore compares US to Jap captures (Jap were slightly lighter).

http://originaltrilogy.com/forum/topic.cfm/THX-1138-preservations-Italian-Cut-available-see-1st-post/post/511598/#TopicPost511598
On page 31, msycamore compares US/Jap to UK captures (cropping was different -- sometimes critically so).

http://originaltrilogy.com/forum/topic.cfm/THX-1138-preservations-Italian-Cut-available-see-1st-post/post/515428/#TopicPost515428
On page 34, msycamore compares US to Jap captures (across 3 laserdisc players). He also noted, thereafter, "... you can clearly see that the US transfer is the best looking, the Jap have a different black level but it also have lots of chroma noise which is almost totally absent on the US disc."

So, I'd say, if your machine is the best available on the forum and produces noticeably improved captures, go for it anyway ... if you will!