They fly A319/20/21 aircraft with very tight pitch, by tolerable for the length of intra-Spain flights. Reliability is not very good but if you get the earlier flights of the day it should be fine (delays tend to build throughout the day).

The most important thing is to do your homework regarding permissible number of bags, size of bags (their hand carry allowance is smaller than US carriers), weight of bags, need for online check on etc. Otherwise everything has a fee. No free food on board and bring your own water.

They are a good no frills option but it is important you understand what no frills entails.