I’ve talked to a couple of people about this, so let me post something more generally to everyone to try to clarify where all the [uN] features should go in verbal constructions.
We split verbs up into several categories based on the number and type of the arguments they require. For example, intransitive verbs, which require one argument, transitive verbs, which require two, and ditransitive verbs, which require three.
The way we encode these “requirements” is by positing uninterpretable category features on the heads in the tree. So, a clause that has an intransitive verb should have one [uN] feature associated with the verb, a clause that has a transitive verb should have two [uN] features.
However, we also have refined a couple of other relevant notions. For one thing, a “verb” is really the combination of two heads drawn from the lexicon: the “big V” and the “little v.” So, when we say that a transitive verb has two [uN] features associated with the verb, that means that between V and v, there should be two [uN] features.
We also have adopted the UTAH, which, among other things, says that if one of the arguments of the verb is an Agent, then it belongs in the specifier of vP. The only way for this to happen is if the [uN] feature that is checked when you Merge the Agent was on the v (and not on the V). It can’t have been on the V, because you can’t have finished the VP and merged v if it was still unchecked.
So, for most transitive verbs, where you have an Agent and a Theme, the two [uN] features on the verb are distributed with one [uN] feature on the v, and one [uN] feature on the V. And, in general, again: Any verb that has an Agent will have one [uN] feature on v.
That means, among other things, that the intransitive verbs that have just an agent (the unergative verbs, like dance, walk, swim) have no [uN] features on V, and one [uN] feature on v.
The other class of intransitive verbs, those that have just a Theme (the unaccusatives), do not have an Agent and thus do not have any [uN] features on v, they just have one [uN] feature on V.