I agree with Doug. We buy some things on BD and others on DVD. Depends on the title and price. As a rule, effects-heavy titles, action flicks, SF-type stuff will be BD while chick flicks and other character-driven shows will be DVD. TV shows we really like - Chuck, Burn Notice, etc. - we get on BD.
Sometimes, if I want it on BD I'll choose to simply wait in the hope that the price will eventually come down or I'll catch it on sale.
This is also somewhat tempered by us not having a BD player on the SD set, and the SD set is the one with surround sound. It's pretty mixed up at the moment. Once we rearrange the master bedroom I plan on getting a small HT system for it, but nothing elaborate.
What I find hard to stomach is when the BD version of a movie costs, say, $7+ more than the DVD. At that point it becomes a value judgment. I find it hard to believe that the mastering/production process is that much more expensive per disc, and even though Sony is the main company behind BD I can't see licensing fees being that much of the extra price. I think the movie industry is attempting to increase profit margins on BD titles.