I've never ridden it, personally but I hear it's fine. One thing to check out is make sure they don't have luggage limits or things like that. I've heard of people getting burned on Ouigo for it but can't attest personally. Also very doubtful it applies to you but as of now, Renfe is the only operator that allows pets so if you need to move a dog or cat, that's going to be the only option.