I'm not sure how reliable most 280 engines are, but I know that ours had a valve job at about 100k and it's just about ready for another one at 202k. Additionally, some parts are difficult to locate for the engine. The car once spent a week in the shop waiting for a special ordered part from Germany. I have not really been impressed with the engine.
On the other hand, the 280SEL is absolutely beautiful. With its European lights and Euro bumpers the car looks like it should. Additionally, it has neat little features like two different horns, adjustable headlights, the reclining back seat, and all of the dashboard labeling is in German. I love that car. Here is a picture: