(This is a spoiler-free ROTK EE post.)
Well, my opinion of the Return of the King Extended Edition was a little better than that of the previous two Extended Editions. I liked the Fellowship theatrical version better than the extended edition, the additions seemed totally unimportant. The Two Towers extended edition I'd maybe put on par with the theatrical version; the additions didn't seem important, but they weren't bad. The Return of the King extended edition is the only one out of the three where I felt that the extended version had useful additional plot developments. (And, at least they didn't extend the ending, which is still awful.) Still, though, it's definitely no better than the theatrical cut.
In the future, when I decide to sit down and watch the Lord of the Rings movies again, I'll probably almost always watch the theatrical versions. That's heresy to a lot of my readers, but I have a reason. Part of the allure of the movies is their excellent pacing and balance... they fit plot, action, and humor all in, in just the right amounts, at just the right times. I think that the extended editions screw up this pacing, adding in more plot without the appropriate amount of extra action or humor (as I mentioned, ROTK EE is the best of the three in not screwing up the pacing, I think). Out of all of the new footage, there wasn't really anything that came to mind as "oh, I didn't just imply that from earlier scenes; that's a new and exciting surprise!"
The new scene with Gimli entering the Dimwalt was my favorite, and the part when they left the Dimwalt was, I think, the worst change made in all of the extended editions. Arwen is still way hotter than Eowyn. And where did Gandalf get staff #2?