Yes, we took advantage of the promotion.
I too voted "Other". I don't have a post-2010 week to enroll, but if I did, I'm pretty sure I would do it. It's the cheapest way I've seen to get a bunch of points.
I certainly am not trying to change your mind, but I did want to say that I feel the DC program is MOST valuable for those who like to travel in the off season to resorts they do not own (like my wife and I do).
I know I am in the minority here, but we did take advantage of the promotion. A couple of the previous posts above give some hints as to why. We started down the Marriott path about 11 years ago with two developer purchases before finding TUG. Then we added three resales. We enrolled everything in 2010 and found we loved destination points. As BocaBoy indicated, it's perfect for those who can travel off-season. We can travel off-season and it is our preference to avoid the summer and holiday crowds. We are within driving distance of multiple resorts and can take advantage of off-season, short stays, adding a couple days to a week, Sunday thru Friday stays when the points are lower, booking inside 60 days for the point discount, etc. We used to go to Ko Olina for two weeks, staying in the lockoff the first week and the one bedroom the second week. Now one of the coolest things we can do is select points instead, throw a few extra points at it, and stay in a one bedroom unit for the entire two weeks. That one thing made enrolling in the destinations program in 2010 worth it. For the last few years, we found that we have selected points for all our units and booked everything using destinations points, staying in many places we do not own. I realize that this may not work for many or even most people, but the flexibility is amazing. It suits us perfectly and with a little planning we get great value for every point we use and occasionally enjoy "splurging" for something a little nicer by using some extra points.
We would have liked to add additional trust points, but as everyone has pointed out, even buying trust points resale is expensive with the additional fees. So instead we added two more unit resales after 2010 to use in addition to our points reservations, and I had begun to look into the possibility of "renting" some additional points when we need them.
Then this promotion came along. As JIMinNC indicated, "It's the cheapest way I've seen to get a bunch of points". We purchaed 3500 points with the 20% off option (10.12/point, no additional incentives), which enrolled our two post-2010 resale units. Since I paid next to nothing for those last two resale units, I was able to add 8,600 points a year to our ownership for about $4 per point. This gives us Chairmans Club status and should keep us there (or whatever the top level is called in the future) for a very long time.
Again, I know this is not for everyone and certainly recognize the value of all the other alternatives people have mentioned here, such as buying resale at resorts you will always use and trading thru II. But for us and how we use our ownership, this was the perfect opportunity to expand our ownership. Since we are just a couple years away from retirement, we will make great use of it.