I watched it when it first aired. 80's Leonardo's voice irritated me somewhat, but the rest were fine. The voice crew wasn't consistent throughout the original run, so it wasn't that jarring to me that some were different. It was nice to hear the old school VAs who reprised their roles, though.
The 80's show was silly, but not to the extent shown in this movie. When it went to CBS on Saturday mornings that it got progressively goofier, but they didn't stop and laugh at everything like a green, shelled Beavis and Butthead quaternity as they did here.
Although I felt they cast the 80's show in a slightly disfavorable light, I still loved the snot out of this show.