I've a feeling we did about 7 years ago (sorry that holiday is a bit of a haze due to gastro issues so it may have been a different car company but they seemed to pool seats). It was not good quality (think tatty Britax supercruiser style) even though we took the best of a bad bunch and I did not feel the least bit guilty when dd threw up on it during the trip back to the airport ! Of course things may have changed since but subsequent trips to Europe have not restored confidence.
I have several times. The Avis car seats have always been like new and they will help fit them. Other companies at Palma airport are the complete opposite though. It's worth registering as an Avis Preferred customer before travelling ( it's free) as you can jump the often horrendous queue.