Running LOP increases the likelyhood of lead oxybromide deposits on the cylinder heads. These deposits become superheated and will induce preignition. The preignition will probably not be perceptable and can lead to catastophic piston or cylinder failure in minutes. Also you are right when you say engine temps will be less LOP as well as ROP. The problem is if you are well ROP and your attention wanders the engine can go a fair bit leaner or richer and chances are nothing bad will happen.
If you are LOP a mixture change either way is bad. A bit more lean and the engine will start surging or even quit. A bit more rich and the engine temps go way up. Your a better man than me if can fly single pilot IFR in busy airspace and still have enough brain cells left to keep a continuos eye on engine temps. In the early days of the Piper Malibu, Piper recommended 50 deg LOP operations. In theory it should have worked but in practice too many folks were melting their engines so I believe they now recommend ROP ops. I have always operated turbocharged flat engines well ROP and have had good luck but I know there are others who swear by LOP ops so go figure
