I felt ANH SE was really well done. ESB SE was great except for Vader's line being changed from an angry, demonic "bring my shuttle!" to a brooding "alert my star destroyer to prepare for my arrival." Also Luke's screaming as he falls down was not needed.

My only real gripe with the SE was in ROTJ when they replaced Lakti Nek with the infamous Jedi Rocks scene. It really detracted from the movie experience and quite frankly didn't fit with the rest of the movie or the trilogy as a whole.