I taught (chapters 0,1,2,6,7) with the book this semester, plus an attentive reader has checked many of the other chapters and exercises. So there have been a lot of minor things fixed. There is no real new material. There are a few places where a sentence or two were added to clarify or explain something that wasn't clear and in section 6.2 there is a couple of paragraphs on computing Laplace of a periodic function, as this sometimes makes it onto WeBWorK problems (I'm guilty of that too) and it wasn't in the book (and it's quite simple). The webwork problem set has also seen a lot of polish this semester especially in those chapters and I've assigned essentially every problem there and did a little bit of moving and simplifying (especially chapters 6 and 7 which were rough).
See
https://www.jirka.org/diffyqs/List of changes:
https://www.jirka.org/diffyqs/changes.htmlBest,
Jiri