I posted a post about getting bumped from DTW to FLL, Oct 2004. I would link to it if the Search was working (is it working now and I just didn't check it?) but anyways...

Our flight was the last one of the day, so we got a (crummy) hotel stay and a couple meals out of our bump, plus $300 ECV x 2.

IMO, I choose the ECV because of the mileage earning. Plus I might want to go someplace other than the US.

As that was my first bump and I was only slightly expecting it, I missed asking about a few things.
1) Amenity pack (toothbrush, toothpaste, shampoo, etc). I think these might be available through the DTW Information Booth (or whatever it is called). And I don't know if you need something (like a note or if you can just show your new voucher) from the GA to get it or not. Not a big deal but would have been nice to have. Reason: our luggage was already on the plane heading to FLL.
2) Ask about possible upgrade to first on next flight as part of compensation. Never hurts to ask.
3) Ask to stay at a specific hotel (NOT Best Western). I would have chosen Hampton Inn (because of HHonors) or Westin (in airport). I doubt I would have gotten the Westin but again, it never hurts to ask.

Things I did to increase my chances of being bumped.
Booked a very full flight.