How many levels are there in the single player campaign? I'm in Act 2 right now, about halfway through almost. Am I about halfway through the game? That's what I suspect.
And how long did it take you to finish the game? In # of hours. And please don't give ridiculous numbers. Also, don't forget to post your level of difficulty.
Something like:
====================
Time taken: 15 hours
Difficulty: Medium
====================
should suffice.