In my experience:
- Critical hits become less intuitive to figure out, slows down gameplay.
- Almost all non-ToB sources of melee damage rely on increasing the risk to increase the reward - this is much worse for iterative attacks, since they rely on being long-shots that'll hit on a high roll for lots-o-damage.
- Skills become less of a ridiculous gamble.

I recommend using it if you have ToB and not otherwise; the first two points can make things too weird for conventional melee builds.