We have just returned from Spain using a scheduled Monarch retun flight.
Our out going flight was on a 'old' 757. The interior looked tired and the leg room was non-existent, fortunately I had booked the extra leg room seat due to a serious illness (9 weeks ago, DVT + PE). The service was very good with drinks, snacks and meals, and the flight was on time.
Our return flight was on an Airbus 321, new aircraft, newer interior and I had managed to book all 3 of us extra leg room £17.50 each, worth the extra. Lot's of room! I am 6ft and I could stretch my legs, we were very impressed with this flight, room, meals etc.
So overall thumbs up for Monarch, but please either get rid of the 757 or update the interior!!