Jon Wells spoke complete sense on it - I'd have three considerations though;
The whole rule should be looked at. The amount of times a televised game is stopped to check an obstruction claim is ridiculous. Today is a great example.
- was the pass on the outside shoulder? If yes, try, if no, then next;
- was a defender impeded? if no, try, if yes, then next;
- did it directly prevent a tackle being made? If yes, no try, if no - try.