I spent some time (and money) looking into this but my ex wasn't playing so I have no direct experience.
According to my solicitor, who is a collaborative lawyer, the big difference between collaborative family law and the usual combative sort is that the two solicitors are actively working together to come to a solution that you both feel OK about. It has an advantage over mediation in that the solicitors are with you all the time so any agreement is extremely unlikely to be overturned in court or challenged by one person's solicitor once an agreement is drawn up. The down side is that this means quite a lot of solicitor time so it probably works out more expensive than using non-legal mediation. On the other hand it must be cheaper than fighting all the way to court.
Only some solicitors are trained in collaborative law so it is easier to do in some parts of the country than in others. You have to be willing to compromise and it requires a degree of trust, and for one person not to feel intimidated by the other. I think probably it is at its best when you have children, as a fundamental principle is that you are both responsible for the children and working for their best interests.
The other things is that when you sign up to it you agree that if it goes wrong you can't use the same solicitor to fight your case. You both have to start again with new solicitors. This gives a strong finanical incentive to everyone (including the solicitors) to make things work.
I too looked at colaborative law and suggested it to my Ex.
As Sadie has already said if it goes wrong you cant use the same solicitors to fight your case in court. My Ex didnt like this as he wanted to be able to take me to court so we didnt use this approach.
BUT, both his and my solicitors are trained in colaborative law and I think that helped. They had actually trained together. Maybe it helped take some of the sting out of the whole process but having never been through this before and having no desire to again I have no benchmark to measure this against.