So without DCT, Extended Leather and Enhanced....you have about a $4,000+ or so spread (I don't have the exact prices in front of me, but they would be sticker given the format of military sales).
So the 2009 has an additional $4K in equipment with 5,000 miles compared to the 2010, but is $4k cheaper at asking price, giving you about $8,000 in difference for used versus new in one different model year.
You may seem some further slide when the 2011 hits, but its tough to really know what the military sales agents have as profit margin in these cars, and therefore what is possible.
I would try to price out the exact 2011 that you want (or one that matches the 2009) to get a better idea of what you may be looking at.
I took delivery of my 2009 in March of 2009, having ordered it over the winter. The few 2008 E93s that left were going for about $5,000 less than mine by the time the summer was in full swing, but then again the 2008 over supply was probably an issue. I take solace in the fact that I ordered the exact car that I wanted and was happy with that. The E93 demo that I did drive before placing my order was nice, but you could tell the thing was ridden hard and put away wet many times. They let me take it out on my own and that what I did with it.....
Tough call......but more enlightened minds may chime in.