I have in the past slipped up and disagreed in front of the kids, and as my psych said to me its important to do so. Children do need to see conflict as often children who do not do not know handle it well as adults... HOWEVER this is a biggy... don't have conflict without resolution. We make it very clear in front of our children that we are resolving it and when their is resolution (which always ends with us both apologising, acknowledging each others feelings and showing intimacy through cuddles etc) we include them in it if they have been there. One thing I will never forget is my psych said to me its important for children to see all aspects of our relationship, but it is important for us to show respect in doing so to each other and our children.
This is so important. DH never saw anyone in his family argue and as such has no idea how to behave during an argument. I saw a lot when I grew up (too much really), so am used to a good barny to get things out in the air and get some resolution. As a result of him not knowing how argue, we often have more argument than necessary as nothing gets resolved from the original one.

I try not to disagree too much in front of the kids, but if I think something is going to far, then I do step in. If anything though I tend to step in more in front of others, as DH has a tendency to "show off' his parenting and goes overboard.