I was running stratholme with my rogue and have noticed one interesting thing:
While killing last one of the 3 mini-bosses that are guarding ziggurats (which you need to disable to get access to the square with the baron) after hitting killing spree i ended up inside the ziggurat with the miniboss not dead yet.
Since i am farming strat, i've seen this happen twice, so as of now killing spree allows you to get through closed doors (at least here).
While not very useful itself, this itself is an exploit and as i see it in theory you could get into some interesting places wile dueling and such...