I just don't like bark in general (or wood shavings). It is too hard to clean/change and I feel it is less sanitary. Wood bark/shavings makes it harder to see things like mites plus with the cages that I use it would make my humidity go through the roof (stays at a constant 60% without misting)
I have used aspen, paper towels, butchers paper, and currently I am using corrugated wrap.
I am really liking the corrugated wrap because it looks better and is more absorbent than paper towels/butchers paper as well as being much easier to moniter and change than aspen.