Even though the DS is my first SLR and I don't have a history of the "old ways", I lean with Tom regarding the aperture ring. I think in general, it's good to have non-electrical means of adjusting the settings - especially physical aspects. One of the most fascinating and wonderful aspects of switching to the DS from a fujifilm digital p&s was that I could zoom with my own hand! I didn't have to deal with that wretched motorized zoom as it slowly went this way and that, wasting battery power along the way.
Also in regard to aperture ring and full frame lenses - I don't like to eliminate options when there is not much benefit by doing so. Every once in a while i think it'd be cool to get a cheap pentax film slr and slap some of my current lenses on it. Since I've become fairly proficient in the ways of SLR, I wouldn't have to be scared of wasting as much film. But, if all I had is a bunch of DA lenses, then I can't do this. And, the DA lenses don't seem to be much cheaper than non-DA, as they were touted to be.
As for the value of full frame vs. aps-c, I'm not sure which is better. My initial reaction is to say full frame, because it's "bigger" and it would yield a larger field of view. I'm also thinking that aperture effects (dof) would be more apparent on a full frame than smaller sensors, since smaller sensors are essentially a crop of the larger sensors.
What's the main distinction of a "D FA" lense? Just that it's good for both digital and film?