I am sometimes cynical, and I look at buying title insurance as paying an extra fee to the title company to "guarantee" they did their job. If a title company did what they are paid to do, then no one would really need title insurance because all titles would be clear. That said, if it is a large purchase, then you probably need to buy it.
Also, per Fredm, watch out. Title Insurance will not protect you in all cases. For example, if there is fraud on the part of the seller. This was discussed in another thread about Ebay sales.
Greg