1) The paper was extremely hard to follow. I read it multiple times and still had trouble following the exact experimental procedures and evaluations that the authors conducted.
2) Relatedly, it was hard to discern what was novel in the paper and what had already been tried by others.
3) Since the improvement in numbers is not large (in most cases, just a couple of points), it is hard to tell if this improvement is statistically significant and if it translates to qualitative improvements in performance.
1) The paper was extremely hard to follow. I read it multiple times and still had trouble following the exact experimental procedures and evaluations that the authors conducted.