Just a quick note this time.
I had set up integrated Lync 2013 with Exchange 2013, and IM in OWA worked great for everyone. But one user complained that he could not see any IM integration in OWA. The user was apparently enabled for Lync as he was contacting me with Lync:)
The solution: The user missed his SIP address in e-mail addresses in Exchange 2013. Not sure why, but adding it manually made the integration work again:)