The Tahei and Matashichi sequences towards the beginning when they split up are basically exactly the same and R2D2 and C3PO in the desert. Even the musical score is very close. Ditto on the space scenes and Midway.

Personally, I didn't have a problem with it -- many of the themes are universal and influence is fine... if anything adding the SFX and different storyline really honors the influencing films. I did get a little jaded when I saw a George Lucas interview on one of the DVD releases where he downplayed the similarities in what was in my opinion a disingenuous way.