Student or Learner
It's right for me to used the sentence - It was my pleasure to work with u? - to the person that it's about leaving.
Would you say It was my pleasure working with you and It is my pleasure to work with you?
Mostly I hear:
It was a pleasure working with you.
'It is my pleasure to work with you" does not work in the context of someone leaving. As Lotus posted, "It was a pleasure working with you" would be more common.
Pope of the Dictionary.com Forum
Do you OK using It is a pleasure to work with you as an introductory?
Yes, I think it is correct and appropriate during an introduction.
If the person has a good reputation and you are fairly certain you are going to enjoy it, you could say "It will be a pleasure to work with you".
Remember - if you don't use correct capitalisation, punctuation and spacing, anything you write will be incorrect.