Trust and Estate laws vary by state, and I simply wouldn't trust software to be accurate enough when dealing with my estate. I had a will done by my attorney, and I was able to adequately divide my estate (including a trust for medical care if my parents are sick), setup charitable donations, and make sure the estate would not be in conflict when I die. I also did a Living Will that specifies what kind of medical treatment I'd like to receive when I die.
If you don't have assets, property, or things you of some value, then I can understand doing things on the cheap. But, I'd have to question why you are even worried about a will at that point?
I think a will is a bargain, and my attorney can easily update or modify my will and do it legally and correctly. Do you really want to have to deal with notaries, any filings, accurate property and personal descriptions yourself, or with a random piece of software?
I am getting married next Summer, and I have complete piece of mind knowing I can change my will and have it accurately distribute my estate. Also, it makes it very hard for any legal challenges to be successful if there was a fight. I think it is worth it.