I really liked having environmental, unaligned creeps that would fight people from all sides in DotA. They'd only really work on bigger maps I think, but on those bigger maps they make things much more interesting (especially Gul'Dan with his super loot drops and the requirement for hugely powerful heroes even to think about taking him down).
Of course, since Beta 1 is all about trying to identify and fix basic functionality bugs and whatnot, I don't find the size of the map or the lack of unaligned creeps disappointing. I just want to let GPG and Stardock know that I really hope bigger maps with third-party baddies will be included in later versions.