I know I have just spent almost 2 years saying "settle if you can," but there are very compelling circumstances where going to trial may be the most effective choice.
Custody and parenting issues create compelling circumstances – there is nothing more important in a divorce than the kids.
If one parent is actively preventing the other from seeing the kids, or from having a normal relationship with them, then trial may be necessary to try and protect the children’s relationship with both parents. There is an over-hyped definition of this behavior, Parental alienation syndrome, but the behavior does exist and often requires that a judge make a final determination as to the parameters of the best custody and parenting plan.
Generally, when this is occurring there is no realistic way to fix it short of a change in custody with the non-alienating parent getting the children. This usually means the hiring/appointment of a Guardian ad Litem, as well as a trial, as it is my experience that a parent who is alienating the kids cannot step back from the fight and so winning that fight is the only hope. This is an uphill battle, but these fights can be worthwhile regardless of the cost, when you consider what is at stake.
One of the symptoms of supposed parental alienation is false accusations of abuse, and generally sexual rather than physical; however, actual abuse does happen and it can be subtle. Often, abusers do not admit to their behavior, nor do they understand it; consequently, many times a trial is necessary to protect the children.
A custody trial may be reasonable if one parent is disinterested, semi-neglectful and just wants to hang on to the kids to keep receiving child support, while the other parent is very involved and the kids want to be with him or her. This frequently occurs as a modification, often some years after the actual divorce. In my experience, this can also arise as a corollary to the children becoming teenagers. Again, in such instances there should be a Guardian ad Litem appointed.
Custody/parenting trials are emotional and difficult for all concerned (even the lawyers), but sometimes they are the only way out of what seems like an impossible situation.