I recently did FAA to JAA IR conversion at FIS.
Allowed myself 3 weeks (hoping for a sneaky few days at the beach)
Was done including test in less than 2 weeks, and that was at a leisurely pace.

No problems. I enjoyed the flying there.

I did my FAA IR to JAA IR in September 2010 in regulation time at FIS, no problems.
In December 2011 I went back and did my Multi IR upgrade also in regulation time.

The only issue you may come across is Seville approach being difficult about the number of IR training sorties it allows at the same time. It just needs organisation and cooperation. Throwing ones toys out of the pram is not the way and you need to take a mature approach.

No matter, I still managed to get done what I wanted to to do with no extra costs. I could not fault the service or the team there.

There is some fantastic scenery to admire too.