Roast pork is a delicious dish when it is cooked well and horrible when it isn't. It is all to easy to concentrate too much on making the skin crispy and resulting in dry nasty tasting meat. As a child I hated roast pork as every time I had eaten it people had overcooked it. I disliked it as much as asparagus which I was served mushy stuff straight from the tin, which was obviously nothing like the true thing.
When choosing your loin choose one with a thick layer of fat without the bone or get your butcher to remove the bones for you (keep the bones to freeze for a stock in the future). Don't let the butcher score the fat for you as this is best done yourself with a sharp knife.