We have just come back from Menorca and used Poppy cars who I can not find any fault with - their service was excellent. Whilst they may not be the cheapest the last thing you want it to arrive at the airport to wait for a bus to take you somewhere to pick up your car - you wont with Poppy cars.
We researched a lot before we booked and could not find a single negative review.
They met us at arrivals and return the car at the arrivals, you pay for half a tank of fuel and return empty so no worry about last minute fill-ups (and you will have plenty of fuel to get to your destination).
Childrens car seats all ready without any sudden 5 Euro per day (had that many a time), roof rack and straps all ready on our car. Helped with the cases. Payment by card.
They were extremely friendly (the kids got 5 Euro for an ice-cream!) Oh and the car was fine too - exactly as specified.
I have fallen foul before and quickly written negative reviews so I am now pleased to be giving a recommendation!