Rare complications. A total hip is a major surgery that can result in complications. While rare (less than 1/100) these can include, infections requiring implant removal, dislocations, nerve damage, persistent pain, blood clots, and even death. Complications can be kept at a minimum by seeing a hip specialist with experience that can share his complication rates with you.
Hopefully few. As total hip replacements are generally very successful, i hope horror stories are few. Though it is a big operation, the hip is one of the easiest joints to replace. Hip replacements have dramatically improved the lives of millions who would have been otherwise wheelchair and bedridden.
Consult surgeon. "horror" stories probably do exist after hip replacement. Fortunately successful outcomes far outnumber poor outcomes. Complications that could lead to poor results may include infection, dislocation, nerve injury or prosthetic related problems. Best to have a thorough consult and conversation with an experienced hip replacement surgery to get the most accurate information.