For me, using the latest FIO board with series one xbees, in a word no. It will work once, maybe a bunch of times in a row and then nothing I do will make it work. So yes it works but not all the time.
If I have a sketch loaded via xbee and then use the serial over xbee the pc can talk all day every day with the FIO/xbee sending lots of data at high speed. But try to upload a new sketch and it will time out.
Hitting the fio's reset sometimes helps if you do it at "just the right time" but not always. My setup is per ladyada, dio3 reset etc.
Now I wouldn't mind if you could not upload via xbee, if for some reason it wan't possible but when it says you can on the "marketing pages" I'd like to be able to do it...
I would love to see the testing that was done on the xbee/fio to demonstrate the sketch upload capability. But I think it was third hand info at best.