Okay, I just spent a few minutes playing around on BA's website. Seems like I just live in a lousy city for Avios miles.
Between major hubs, there is decent availability, but in and out of Pittsburgh will only work for about 1 out of 20 dates.
I spent some a few more minutes playing around with BA's site and I figured out the mystery. Maybe it was obvious to some, but I will spell it out anyway. IF, and I stress IF, your city has lots of AA flights, then Avios will work well for you with its awesome short haul values. However, if you live in a city like PIT that has lots of Delta and USAirways but very, very little AA, then Avios kinda stinks for you. The more AA action you have in your city, the more likely your Avios are to work for you. So for instance, I can't get more than a 5% availability out of PIT even to major hubs like Chicago, NY, and Toronto. But if I want to go from PIT to DFW, then 95% of the dates are available. Why? Because DFW is AA's most regular flight out of PIT. So it ALL depends on how much AA flies the route that you want. If there are only one or two AA flights a day for your route, chances are you will NOT be able to use Avios.
This is what I was able to figure out over the past 20 minutes of playing around. I'd love to either hear some confirmation or (even better) to be proven wrong.