Just got back from Spain. Journey went smoothly, and JK provides a perfectly respectable, punctual and good value service.
No problems with *G check in, lounge access and priority baggage handling - but beware of long lines at MAD airport ticket counters. Fairly spacious lounge in Madrid, free booze and bar snacks, 1 internet PC.
Dog-eared MD-83s were full and seat pitch was tight. But inflight service was friendly. No food or drink (unless you count a boiled sweet) from MAD-AGP. Beverage service on the way back.
All-in-all it was excellent value for EUR69 incl tax. And *A miles too (if they ever get posted...)