To some extent it depends on the formality of the occasion. But in general I'd stick with no 1.
No 2 is probably OK but from a strictly literal point of view the fact that it 'was' a pleasure could be implied to mean that no longer is it a pleasure to have talked to you.
3 & 4 are concerned with seeing not talking and hence from a literal point of view don't really fit. 'Nice' is also a sort of wishy washy sort word when you can think of nothing better to say.
Student or Learner