Some of the first roller rockers that came out had needle bearings to run on the shaft as well as a roller tip. The needle bearings failed prematurely, and as far as I know everyone quit making them. The roller tip rocker is still widely used. fhsmith, you are right about the guide wear issue. Generally speaking, the higher the lift of the cam, the more the rocker puts side pressure on the valve. A rule of thumb that many engine builders use is to put roller tip rockers in anything with over .600" valve lift. If valve train geometry is near correct (valve stem protrusion, etc) normal production rocker arms will not cause a lot of premature wear with near stock cam lifts, but roller tips sure can't hurt. Some say the roller tip rockers are slightly noisier than stock, but my ears aren't good enough to tell the difference.