I am wondering if you are sticking to your rules and disciplining your kids accordingly (which at my house always seems to result in my kids saying "that's not fair" and throwing their little fits and talking back), but maybe your husband is letting things slide, so the kids are not talking back etc to him? Maybe his perception is that the kids are acting "fine" when in fact they're doing a whole lot of things that are not ok at your house. And then when they get back to your house, they've got bad habits that you have to break them of... resulting in you being the "bad cop" to your ex-husband's "good cop."
I don't know if that's the case, of course, but I know that I tend to discipline my kids for things that my husband doesn't clue into. If you think that might be the case for you, my only suggestion is to try and come up with a list of things that the kids are NOT allowed to do in your home, and get your ex to agree to that same list (possibly this may end up meaning some things get taken off the list - whatever, as long as both parties are using the same rules). I don't think it matters HOW the kids are disciplined, as long as both parents are taking action on the same issues. It seems to me that consistency between both homes would help.
Anyway, I don't know if this was helpful, but it's what sprang to mind for me when I read your post. Good luck and let us know how it all turns out!