The biggest error I've seen that no one has mentioned is Luke's X-Wing on Yavin. We see Luke getting into an X-wing with a solid red stripe. According to this site only one X-wing and one Y-wing was built full scale. (Check out the next page, it details one SE change the pissed me off - the use of Red two only in scanning the X-wings for the "improved" BoY).

However, during the entire battle, Luke is piloting a X-wing with a broken stripe

Finally, back at the Rebel base, Luke is seen exiting the X-wing with a solid stripe.

I didn't see this on that site listed above.

Also, how about the inaccurate Death Star plans? Technology at the time refused to allow an off-center circle put inside another circle. These are two things I was surprised weren't changed for the SE. After all, only a single X-wing was used for the battle, with only changes to the stripe done(the tell-tale number stripes pegging it as Red 2 and the rust give it away). Given that changing the stripe is easy, I fail to see why it wasn't.