Because living trusts are not under direct court supervision, a trustee who does not act in your best interests may, in some cases, be able to take advantages of you. (In a probate, direct court supervision of an executor reduces this risk.)
In addition, the cost of preparing a living trust could, in some cases, be higher than the cost of preparing a will. However, it depends on the particular estate plan. The difference in cost may not be significant if the estate plan is complex.
Also, keep in mind that a living trust can create additional paperwork in some cases. For example, lenders may not be willing to lend to a trust and may require that real property be taken out of the trust (by a deed) before they will agree to a loan on that real property.