Vueling is a great little airline
I have had the fortune of taking a number of flights on Vueling post their merger with clickair
They have a good product. I liked the new style of seats with the magazine rack higher up, giving what felt like more leg room.
Their prices were good too and i have used their hub for transits. This is the new terminal at BCN. It worked very well. I connected TFN - ZRH via BCN and also did PMI - BRU via BCN. And i earned BA miles as i booked sectors via IB code on GDS for some of my trips.
They are travel agent freindly which is a bonus too.
Good on Vueling for seeing the gap at Cardiff. Fingers crossed this works well for them and the airport