DMD can implicitly convert class pointer to the bool. Is it bug or terrible feature?

[Maxim Fomin]

On Sunday, 24 November 2013 at 14:16:39 UTC, bearophile wrote:
> Maxim Fomin:
>
>> This is neither bug not a terribale feature.
>
> I think the implicit question of ilya-stromberg was: how much 
> bug-prone is this language feature?
>
> Bye,
> bearophile

OK. What are the problems with converting class references to 
true when they are not null and false when they are null?