This week, Michael Jackson's will was filed in the probate court. It was surprising, actually, that someone with his assets died with only a will. In California, it is common for those with property (even just a home) to create a living trust so that their assets will pass to their heirs without the cost and delay of a probate proceeding.
There are times, though, when probate can be an appropriate place to settle an estate, and Michael Jackson's might be the poster child for these cases -- when there are messy creditor claims to sort out. Like a bankruptcy court, a probate proceeding is place where creditors and their claims (and we won't even mention the guardianship issues being raised right now) can be sorted out by a court, in a set period of time and with finality.
The AP has published a good article if you're trying to sort out whether a will or trust makes more sense for your family. Briefly, though, if you live in a state (like California) where probate is expensive and time-consuming, if you want to leave everything to your kids, if you own a home, and if you don't have complex credit issues, a trust is generally a great long-term investment.
For practical, straightforward recommendations on estate planning options, see The Mom's Guide to Will and Estate Planning, by Liza Hanks (Nolo).