As with any soldering procedure, you must get your process right. But when you do, it is as good as other methods. When you go to details, all solders have good and not so good properties. Notable downsides for bismuth alloys have low surface tension, so parts don't self-align as nicely and fall off more easily if doing double side reflow without glue. Also, those used to be expensive and they don't tolerate lead pollution (but you are supposed to keep leaded and non-leaded separate anyway), but those issues shouldn't be problematic nowadays.