What's interesting is that the AAward system was just upgraded to be much more useful and easier to see the potential availability. When I was booking some award seats around this time last year, the NW site was reasonably good to help me find what I wanted and get the tickets booked. Their system will give you the month calendars if you use it for a little while, but I'm not sure what kicks into that mode. (That mode also only works with NW availability, and you have to poke around on your own to find out about CO and DL and other codeshare partners.) I seem to remember that it came up after I'd searched a few times trying to find saver awards and couldn't get any results. I just had it come up for RDU-AMS which is telling me that there are F seats available at 50K miles on 10 different days through the end of the month. I'm still not sure how to get it to show up, but I got it to come up when searching from the "more details" award page and selecting "Search PerkSaver Award Only".

I haven't tried US since the HP merger, but the old system was reasonable to find availability based on the mileage you wanted to use except that it couldn't support split awards (saver one direction, anytime other direction).