I started reading the books about 15 years ago. I read the first half of the series in paperback. Even with the paperbacks (subsequent editions) I would find the occasional error and I always found that annoying.

Then I got to the point where I was purchasing Hardcovers as they were published(starting with Path of Daggers). With these, I was finding more errors which I found increasingly annoying. Then Towers of Midnight came out. Hands down! Most typographical errors I've seen out of them all.

I was also finding them every few pages. At some points I found more than one on a given page.