I ended up going with white. I chose Renate Ljuv curtains from Ikea. They're white, sheer-ish, with a modern floral pattern. This will allow light to come in, be neutral to go with any bedding or wall color we choose, but also patterned for a little visual interest.
I went with black lightweight inexpensive hardware to hang the curtains. I may regret the decision to go with such cheapies (less than $10/window), but if I need to buy new ones then I can do that later. For now they're working fine.
Jason hung the rods about 2" below the ceiling. Hanging curtains higher than the top of the window can give the illusion that your ceilings are higher. Since our 2nd floor has lowish ceilings, I'm hoping this trick will help a bit.
Ikea curtains are designed to be hemmed with simple ironed on hem tape, so I did each pair of panels individually (since the windows are all different heights). It took about an hour to get all the curtains done and hung.
I think the look is great! The curtains add a little softness and coziness to our room. I think we will end up changing the paint color (not sure what color yet) and adding a few things to the space to help with the clutter.
Photography Note: I took an "after" photo earlier in the afternoon, but then I realized the room was a mess and I didn't have time to clean it until the kids were in bed. So this is a night photo, which explains why the light is so yellow compared to the "natural" lighting in earlier pics. I was too antsy to wait until morning!