I'm not an estate planner and do not evaluate the quality of the will kits available at various book stores or on the internet. I have heard from colleagues who draft wills and trusts that these form kits are often flawed in substance and fail to comply with various technical requirements of state law or do not really offer the tax benefits advertised.
As a probate litigation attorney, I have another perspective on these will kits. They are easier to challenge than a will or trust prepared by an attorney and where the execution is overseen by an attorney. I have handled multiple contests of internet wills in Texas and every one has resulted in a relatively quick, and favorable, settlement for my client. The problem for the proponent of such wills is that there is not an attorney, and the attorney's staff, available to testify that the testator appeared to have capacity and did not appear to be subject to undue influence. Thus, you are often left with only the proponent and the proponent's friends - or total strangers who don't know the testator and aren't trained in any manner to evaluate capacity - to support the will.
Keep that in mind if you are considering using an internet will and there is even the possibility of a contest. I've challenged several for clients where hundreds of thousands of dollars were at issue. So far I haven't handled any contest of an internet will where the estate was valued in the millions of dollars. But I suspect it won't be long as the internet will kits become more popular due to constant advertising. People are often tempted to be penny wise and pound foolish. That is the perfect description for someone who would use a will kit to direct the disposition of a seven figure estate.