A postal money order is good for tracking, but many people purchase money orders from stores like Wal Mart because they are cheaper than a postal money order (I think Wal Mart charges 45 cents while the post office charge something like 80 cents?).
You can't cancel easily it once it's purchased (Travelers Express who issues most of the non-USPS money orders I receive, charges a $12 per money order tracing fee, and that doesn't even put a stop payment out). WHen you receive it, you treat it just like a check. You can deposit it in your bank, or cash it. You just endorse the back like you would a check. Once it's cleared your bank, the funds are yours (just like a check).
I only accept Paypal and money orders. Most people pay through Paypal, but I still get the occasional money order.
Robyn