1. They move the boat with their bodies often using a virtually stationary paddle as distinct from moving the paddle with their arms.

I agree with you that using your "core" (aka body, specifically abs & obliques) is important, but I wouldn't describe it as a stationary paddle or neglecting your "upper body" (aka arms, specifically biceps, triceps, pecs). Utilizing your core AS WELL AS your upper body is the key for paddling. Really good boaters can utilize their cores to (1) provide strength into their strokes (forward, draws, sweeps, etc.); (2) allow less fatigue in their upper body muscles (e.g., arms, pecs, etc); (3) lean their boats for longer, more extreme, and with better proficiency; (3) move the boat (e.g., in pivot turns, during boofs). However, using your arms/upper body is ALSO important. I would say that really good boaters can use their core AND their upper body to move their boat and paddle efficiently and effectively.

2. They are far more aggressive in terms of taking more strokes; driving rather then drifting.

I also agree with your general point here. But instead of saying their are "far more aggressive," I would say that they are "far less passive" as well as "confident." A good paddler knows where they wants to be, and they get there. A good paddler also knows that letting the river take you were it wants isn't always they best decision. There is a different between "running a river" and "making it down" a river. Good paddlers look to take/break down rapids in steps (like a slalom course) and often will eddyhop to make sure they have the best lines. Too often not-so-really-good paddlers just bomb down or float down without THINKING about the river. Also, really good paddlers utilize their core (see above) and thus each stroke (or series of strokes) is strong when they need them to be. 

As others have said, really good paddlers often don't take unnecessary stokes, but when they do (e.g., boof strokes) they do it aggressively or confidently.  Likewise being overly agressive, bombing down a rapid without thinking, and needlessly using your energy are not characteristics of really good boaters.

But most important, really good paddlers are not intimidated by the river while they are paddling. Being in a passive position (body back, paddle up or not stroking) is bad. You are not ready for what the river is going to throw at you and you are not ready to react. Really good paddlers are aggressively (or not passively) ready for the river.

3. They tend to work in the bow more than in the stern.

Yes. While there are times to work in the stern, your most important place to work is in the bow. Why? (1) Most importantly, because you are facing forward (hopefully), your strokes are most efficient in front of you -- you have more power, more control, and more efficiency, and (2) also, because (assuming you're going forward) you are leading with your bow -- and it will hit most of your lines first, so that is where you want to concentrate your work/attention.

4. They read water very well and use it well.

Of course (this is your "duh" point). As a really good boater-friend of mine says: "Only follow my line if it's good." Reading water well is VERY important because (1) it helps you find lines, (2) it helps you minimize your effort (aka using the water), (3) it allows you to find places to boat-scout (aka finding micro eddys), (4) it keeps you safe (aka you know where the bad spots are), and (5) it allows you to find play (aka finding good play spots).