I have a lot of board game geek friends that don't role-play: should the “D&D” on the box mean anything to them?
Not really. You know how some people say that 4E is nothing but a boardgame? Well, Ravenloft and Wrath of Ashardalon is the result when you actually distill the rules down to a boardgame level. There is no roleplaying in there. No need for a DM. (The monsters have a pseudo-AI on the card that runs them.)
Here is a nice review that matches the feeling I got the couple of times I have played it.
Are there characters in the box they can bring to a weekly 4E or Encounters session?
Nope. The second page of the article I linked above has a picture of one of the "character sheets." Stripped down is an understatement.
Do they come with a little sheet that says something like “if you like this, try these products for the full experience”?
I don't recall. I would be surprised if they didn't.
Is there anything in the box worth using at my weekly games or the Encounters sessions I organize for my FLGS? I see they come wit minis. Are they to the same scale as DDM figs?
They are to the same scale IIRC.
I am not sure. I am not a connoisseur of plastic, so I can't help you.
Is the game board useable with 4E?
Probably, if you wanted to use it as a dungeon map.
Are there any useable rules or scenarios I could use?
There is a rule book, and a scenario book that has a bunch of scenarios in it. Here is an example of some of the flavour text that comes with the adventures:
Here is the basic description:
Search for the Sunsword
The Heroes seek a magic sword’s missing piece. Once assembled, the legendary Sunsword becomes a powerful weapon against the evil threatening Barovia.
Goal: You must recover the last piece of the Sunsword from the crypts below Castle Ravenloft.
Number of Heroes: 2 to 5 Heroes (group adventure).
And here is the "box text"
Ages ago, Strahd’s attempt to destroy a powerful weapon left it damaged but not broken. The magic remained, dormant. Although the hilt of this blade is lost in the crypts below Castle Ravenloft, a young servant escaped with the weapon’s enchanted blade. After being passed down through generations, one of you now holds the blade of this ancient sword. If you can
reunite the blade with the original hilt, the power of the Sunsword will return and you will gain a powerful weapon against Strahd and his evil minions.
Hope that helps...
Oh yeah, here is the preview, which includes a pdf copy of the rules, in case you are interested.
Dungeons & Dragons Roleplaying Game Official Home Page - Article (Castle Ravenloft Preview)