I've found it that it is 'normal' to run all the way to the M on the gauge...but thats not good, its way too hot. You should do something to bring those temps down. Maybe you should turn your AC on so that the low speed fan cuts on and cools the engine. If you have an early bird try installing that pontiac air dam to direct cool air to the radiator, or re-wire your fan.
*never mind, i just saw you have a late model SC. What i do on mine is turn the climate control on so that the low speed fan cools the engine. Even then, whenever i slam th gas or cruise for a long time the temp starts creeping up so I rewired the pusher fan on the outside of teh rad to the 'trac asssit' button and that helps it cool even further. Also, you could try flushing your coolant system, adding some water wetter and a lower degree thermostat...i got a rober shaw 180*....it helped...but temps went back up after a while.