Don, $800 for a Model E is a pretty good deal. At the end of CRASH-B they sell the rowers (which are pretty much brand new), and the Model E goes for $900-950 (compared to 1200 or so). If you end up looking at it, check to make sure the rollers aren't clicking (they could just be dirty, Windex fixes that), and that the chain/handle returns nicely. The previous owner should have maintained it regularly, which includes cleaning/lubing the chain every month or so.
My trainer now has me doing the rowing machine as my cardio in between resistance training exercises.
I can do a pace of 2:20 for 500 meters essentially forever. But once I go sub 2:00 for 500 meters, I tire out real quickly. One of these days I'm going to show up for training with an Evinrude and that should fix the "getting tired out problem."