An update: like I said, I really don't want to do something outdoors. Another option with my apartment is that my north wall is not flat across the entire face of my apartment. I've got a chunk of it that sits further out due to a fireplace (in the living room) and a closet (in our 2nd bedroom/office). And thus, a west-facing option for an indoor antenna.
So, after doing some more reading, including threads in this forum, I bit the bullet and got an HDHomeRun Dual tuner. I was already going to get it from NewEgg due to the price, but they also had a combo offer for a HomeWorx indoor flat antenna, which made the $30 antenna free.
The antenna came with 10' of coax, and despite it saying it's multi-directional, I still taped the antenna to a west-facing wall in the middle of the closet. I got the whole thing up and running (more or less*) with Windows Media Center.
The worst signal strength I'm getting is ABC at around 67% (it's actually coming up on two different channels, according to the HDHomeRun, with the other at signal strength of 90%). It's running fairly smoothly on WMC right now. I'm rarely seeing any artifacts, but it does look like the occasional frame is lost. Either that or it's lag from the HDHomeRun itself.
I'll keep moving the antenna around to see if things can be improved further. Also, I want to investigate the coax that came with the antenna to see if an upgrade is needed there.
So, thanks for the help and opinions, and apologies for the change of plans halfway through.
*More or less: Windows Media Center refuses to update the guide. Apparently this is a common problem with no easy solution. Thanks, Microsoft!
Edit: It looks like WMC only found the ABC channel with the worse signal strength, so I manually added the better one. More thanks, Microsoft!