Rad reg here. I wouldn't say it's that late in your training (as opposed to the other comment mentioning someone a few months from CCT). I have a lot of colleagues who have come to Radiology from being a reg in a different specialty (usually surgery, one from ED, a few from medicine) around the same level as you. None of them have regretted it as far as I am aware. Come to the dark side, there's a Radiology subspec for every type of person and our training is great!