Are there any reports of ACLs gone wrong? I mean, is there any additional risk beside the mentioned misconfigured POSIX permissions. If there isn't, I don't see the benefit of deactivating ACLs. Especially, since most apps only modify the POSIX permissions (I guess most developers don't even know about ACLs). The only app I know of that modifies ACLs is the Finder...

I tested the script and it revealed way more than 1000 files with ACLs. Most of them somewhere in my User Folder. I guess it is because I have many network shares, which I change quite often.

There's another point with ACLs which should be mentioned in this context. You can actually share files with people that do not have a user account on your mac (see the permission rights in the Get Info window). Actually you can share with anybody in your address book. In my understandig, this is stored in the ACLs, since this is not a standard POSIX feature. So, meddling with ACLs can break your shares.