What you have to remember is that if you have a little bit of background or experience in legal or other matters like this, you can fill out these forms fairly easily by yourself, without the hassle of using an online forms website. However, if you have no experience in this field, or are a bit nervous when it comes to these things, this could be something to consider.
One thing to remember is that online form sites like Legal Zoom is that they are NOT lawyers. They are not legal counsel, and they can not give you any legal advice. If that is what you are looking for, than it might help for you to seek the advice of an actual lawyer. If you are wanting to set up an LLC, or INC, these processes are relatively simple and can usually be done yourself. But, if you are doing anything more complicated, that you might actually need to check with a personal lawyer on, online legal form sites are probably not the way to go.
Just like many other things related to creating and running a small business, using an online legal forms site is a decision that you are going to have to make on your own. Weigh your options carefully, and make the decision that is right for you.