The feat is worded to specifically allow you to KEEP the AC bonus from the buckler regardless of what you are doing with the other hand, whether that is to cast spells or wield another weapons with it (including 2 handed weapons). Essentially, you never had to worry about losing that shield bonus.
Yeah, this seems to be perfectly clear and I have no qualms about it.
This also lets classes that require the offhand to be free (or a monk, which can not use a shield without losing their features) to use a buckler regardless, and keep the AC bonus.
This is what really bothers me. It just seems to be redundant with the default rules. Just because you are wearing a buckler doesn't mean either of your hands is occupied. It is strapped onto one of your arms. The respective hand is still free, isn't it? heck, in the buckler's descriptions, it mentions using it with your "shield arm", not a "shield hand". Having a buckler does not hinder one's usage of, say, crane wing or the precise strike deed in any way.
What I'm trying to get at here is that a very literal interpretation of this feat, at least in my opinion, allows the player to have a "virtual free hand". The player wears a buckler, and the hand of that respective arm is "is considered free for the purposes of casting spells, wielding weapons, and using any other abilities that require you to have a free hand", even if that hand is already doing something else and not actually free, such as spell-combat, holding an object, etc.
This interpretation is, obviously, very questionable. Hence I am here asking for opinions from fellow gamers. Do you think this interpretation is absurd? Is there any official ruling for this?