I've messed around and put formula on a spoon a couple times for him to see how he reacted to having the spoon pushed in his mouth - he's been ok with it every time. He also sits up ok in his high chair so I thought it would be ok.
From the first spoonful, it was clear that he loved it, even though he was quiet. He had no problem with the spoon in his mouth and tried to grab for it and stick it in his mouth - I guess we weren't feeding him fast enough!
When we tried again the second day, he did even better. He had a big smile on his face when he saw me coming towards him with the bowl and spoon. He smiled and babbled the whole time he ate... so he got a little messier, but he didn't seem to mind too much!