Surprisingly enough, I've actually been enjoying Return MORE the past couple of times I watched it than I maybe ever have. That's not to say that I still don't think it's the weakest link of the trilogy, as I have since the first time I saw them when I was 9, but I do enjoy it.
I'm sure most people here know exactly what bugs me about ROTJ the most: the completely ridiculous, time-wasting, irrelevent to the plot Jabba the Hutt sequence at the beginning. Even then I still don't find it painful to watch, but I do shake my head at it. If they had found just ONE significant way to relate it to the plot of the rest of the movie, it might have been justified. But, no, it's just a huge half hour of one plot, and then we suddenly shift gears and have an hour and a half of a new, unrelated plot.
The Ewoks don't bother me. I actually really like them, and I cringe at the thought of it having been Wookiees instead. But I don't know if that's just because of the terrible Wookiee battle in ROTS, which was the point of the film where I entered a coma... on two separate theatrical viewings! But to get back to the point, I find the Ewoks entertaining and even somewhat plausible.
What I don't find as plausible is the idea of the subterfuge the Rebels took. Obviously the plan was to keep unnoticed until their strike on the shield generator, which was why they were so intent on killing any Imperial who saw them. But it does seem a bit unrealistic to me that no other Imperials would notice that a dozen of their troops are no longer calling in or that there were wrecked speeders all over the landscape. That should have ruined their element of surprise right then and there. But then again, since it was all just a trap to begin with, I suppose it's okay.
The middle section does drag a bit, but the final act makes up for it. It's Luke's story, plain and simple, and that's where the film really, finally shines, and it's probably the only part of the film that begins to measure up to the precedents set in the previous two movies.