During my brief subscription before I canceled it (after they restricted all the AA itin functions), I had found it didn't list any UA award booking buckets (R/X/O/I/N/E)... and for revenue buckets, as said you can find them on united.com.

Since aa.com doesn't list fare buckets, it was a little more useful for them, and listed AA award inventory too. For a UA only flyer, I would never recommend it unless you wanted the buckets and rules a little faster and were willing to pay for that.

There was MUCH discussion about it in the AA forum, and then moved to TravelBuzz here. That thread should tell you everything you ever wanted to know about it and a whole lot more!