I did this with a 68kg ‘gal’, going up about 10 lots of 10 stairs (each floor had two stair cases going to it, 5 floors) five times. That was once up the 5 floors and once down, which equaled one go (up and down five floors five time). My legs burnt a bit afterwards, but the next day there wasn’t really aything to be worth wankin over, if wasn’t that good. I hear step ups (obviously with weights) are much better.
I felt it very good on my fitness, as I was breathing much more than I did when I went running.