I thought he was okay in it, really. Kind of a dry-witted smart-ass, but nothing over the top or annoying. Reminded me of Seth Green in those Austin Powers flicks a little. Some nice under-his-breath comments or asides (like his bad luck/lousy timing at being involved in all that was going on). He didn't bother me at all in this movie.
He was a hacker type, and, yes, he did have a Cinema Display in his apartment.
He was this movie's Zeus...a regular schmo drawn into the action somewhat against his will, but who steps up when it counted. But he was somewhat comic relief, poking a few holes in McClane's whole "tough guy" persona and gruff outlook.