Quick report: I've been using the Milwaukee 2504-20 for just about everyday this past week on the window project (not as easy and straightforward as I was expecting). It is really nice to have the adjustability it does, this being my first torque adjustable drill and first cordless one, too, and is quite comfortable to hold in different positions (down low, up over my head, etc.) The batteries last for a good long time; after the second full charging up of the compact 2.0 Ah (the first time was when I first got the drill) it has not stopped or run out of juice, yet. The 4.0 Ah battery seems to go on forever, not having to recharge it since first getting it. Actually, the 2.0Ah battery has been what I've used so far except for a short while to try the bigger one. Nice!
My only criticism is that I wish the LED light were lower down the handle and aimed up slightly to clear the chuck better; the chuck creates a shadow right where the light is needed most.
This drill is very powerful, certainly all I really need for just about any task I would do. I'm glad I looked at this vs. 18V drills; I certainly don't need what they offer, power-wise, and the size and weight savings is great with this 12V model for my (getting older) hands and wrists. Having a 1/2" chuck is nice so I can use all the same bits and other accessories that I have available for my Dewalt DW235G corded drill. At first I was looking at 3/8" chuck models, but then realized the price increase to the 2504-22 kit was well worth it, as the higher price gave me two much higher capacity batteries and a hard case instead of the two 1.5Ah batteries and soft bag that comes with the 2407-22 kit (both come with the same charger). Those items, alone, cost well north of the difference in price, and I would have bought the higher capacity batteries, anyway, so this really saved me money while giving me the better drill at the same time.
Thanks for all your advice.

I hope this helps someone else, down the road, looking to buy one of these.