I was most surprised to see how much of the physical action was actually performed by Harrison Ford. People tend to forget that when you're a 65-year-old man, it's no small feat to be repeatedly thrown to the ground, dragged through car windows, and knocked around in fight scenes.
They also employed far more practical sets and effects than everyone gave them credit for using. It wasn't uncommon to see people slamming the film for being nothing but "greenscreen"- but that simply wasn't true. Two things no one seemed willing to acknowledge were, A) It's been 20 years since Last Crusade, and B) The original Indy films were not "old school" at the time. (Even if they had been, what constitutes "old school" in 2008 is still not going to be what it was 20 years ago.)
It's interesting to note how differently today's audiences view those first three Indy movies. Unlike today, Raiders was not considered an overly-serious movie in 1981. It was a non-stop rollercoaster ride and contained a great deal of humor. In short, it was fun- especially in comparison to the gritty action films of the 1970's. Today we think nothing of the movie's finale, but it was pretty over-the-top at the time.
I think the problem so many younger viewers had with Indy 4, is that Spielberg basically made it for 1989 audiences. If this same film had been released then- or even in the early 90's- I doubt there would've been a backlash. Gags such as the library, rubber tree, and fridge are straight out of the 80's, and would've likely gone over extremely well.