This was my first drive-in experience and our party consisted of two adults and an infant. It was great! Lots of people with kids and if our baby cried, we just rolled up the windows to not bother others. Picture and sound quality is great and the $6.75 per adult charge was fine for me. As it was our first experience, we didn't come super early and had to wait in line for a while -- but didn't miss too much of the movie.
I am docking a star only because I think the mechanics of the entryway could be a little better - our line only had one attendant for two windows (both sides of a ticket booth) and while she did a great job, perhaps things would go faster if there were two attendants/registers in the booth.
All in all, wonderful first experience! We will be back.
My tip: Bring exact change for your party so you can get in faster (and the attendant will appreciate it, too!)