I'll start by saying I LOVED the performance and fuel mileage of the small diesel (RAM Ecodiesel). So yeah, I considered the 3.0L Duramax Diesel. However, my less than stellar experience with initial cost, reliability, emissions, and actual cost of ownership with the Ram EcoDiesel sent me another direction. I was a guinea pig for one baby diesel, I didn't see a reason to volunteer (much less pay) to be one again... Now, in 4-5 years if the 3.0L Duramax Diesel proves to be reliable and ultimately worth the initial investment, I'll be all in, till then I won't be rolling coal.
IMHO, the way things are going with the EPA and politics in general, I'd be surprised if any of the Big 3 continue to offer a small diesel in a half-ton truck.