Not burning with your flamesnot to flame you but you regret buying that lens because it's not the lens for you and not because it's not performing as you'd expected...
it should be something like, "i regret buying 50L coz it's not sharp wide open & it has focus issue"...

In fact, if I bought a L lens simply because it has a red ring, then I only have myself to blame if find out that its quality is not as good as expected. Red ring lust is no excuse.