There's been changes in oil over the last few years, namely the reduction of ZDDP in the current grade oil, which is SM. You just have to make sure to add the break in lube and perhaps some additional ZDDP during break in. Once the cam has been run in, it'll be fine.
I've heard the horror stories of "the oil ruined my engine", usually from guys that had a so-called "professional" engine builder do their work. In many of the cases, it's the builder not wanting to fess up to their poor workmanship. Other cases it's poor quality or mismatched parts. I've been putting SM grade oil in flat tappet engines since it came out, with most of them seeing far more miles than the engines that seem to be having problems, haven't had the first failure yet. If it makes you feel more comfortable adding the extra during regular oil changes, do it. It won't hurt anything. Just make sure to use an additive meant as a regular lube, and not the break in additives, as they can cause pre-ignition as well as premature plugging of the oil filter, which can lead to early engine failure.
