I had the same problem. Replaced the coolant level sender and all is well. Also, the coolant level must be kept right up to the fill mark or the coolant light will come on while cornering.
My temp gauge also bounces around and like yours, never passes the midpoint, and usually indicates it's running a tad cool. Then again, almost all my gauges bounce all over the place and go in and out! Will eventually pull the whole cluster and check it out, but it's kinda low priority right now.