I had an early e38 (1995) 740i for about 2 yrs, which had over 221,000 miles on it when I sold it and was still very tight and drove superbly. One of my favorite cars ever, the 740 is certainly the one to get imo, I drove a 728 once and it felt much the lesser car. They don't seem to rust, but suspension needs checking carefully as they are of course heavy cars, so bushes etc can wear. The nicasil issue, is pretty much not a concern now, as many engines were replaced under warranty/good will by BMW. So they car you go to look at may have an engine that has done considerably less miles, than the odometer readout.
My main thing I would check if buying another is the cooling system. They can over heat if the coolant has not been religiously maintained. I would probably replace the water pump and radiator anyway on any 740 I bought, so peace of mind.
Sometimes get bulb warning lights on the dash, this is often due to rain water getting into the rear light clusters and causing a short that trips various dash lights.
They are great cars and a real bargain now, a very good choice imo.
