's response boils down to "don't use state variables as a replacement for class variables when doing OO". I agree with that. The argument that it will be easy to make this mistake is false though as p6 OO looks visually a lot different from p5 (method foo() vs sub foo() for instance). I am not saying caution isn't warranted, but this is just once case that doesn't negate the usefulness elsewhere.
Update: I reworded my response to be clearer but I believe the spirit of the message was left in tact.