The difference may be small between the two bolt patterns, but the 114.3 rims will stress the 115 spaced studs when the lugs are tightened. Sorry to get nerd on ya'll, but the lugs are most likely designed to be generally pre-loaded with only an axial loading (lug tightened) and then whatever the weight of the vehicle is and the resulting bending/shear (the loads when the wheel is touching the ground and the weight of the car is on it).
Through each revolution there is a stress in each stud that the vehicle is designed to. 114.3's on 115's add another component to the stress and add to it. Sure there are safety factors, but you're rolling the dice.
Even though we're talking about such a small amount here, it would be easy to significantly increase the stress in a piece of steel without seeing much deformation.
Sorry for the rambling - end advice...use the bolting pattern that it was designed for or you're looking for trouble. Not immediately though...this would most likely end up in a fatigue failure over several years.
If you have 114.3's on 115's it would probably be good to make a habit out of checking your studs a few times a year by completely removing them and inspecting for fatigue...or just replace them often.
Trust me...you don't want your wheel falling off at highway speeds. I read one police report where a rear wheel flew off...it seems like a wild ride!
