I paid $1000 to a lawyer for an operating agreement. It was fine.
For my 2nd LLC I just copied a free template (different than my expensive lawyer'd one) since I now had a really good understanding of what needs to be there.
At first yes it's scary to think you might be getting it wrong, but you learn that it's not rocket science. It's basically the agreement between the members of the corporate structure. I haven't read the NOLO one but I bet it's good value for money.
You will generally have to present the operating agreement to the bank to open a business account, to get business financing, maybe for insurance, stuff like that.
My experience (IANAL) is that for friendly partners, the nolo template is going to be fine. If you're selling shares to folks that you don't have a history with, you may want to have the assurance of expert, personal legal advice from someone you can also go back to with future concerns. And for that kind of bigger LLC anyway, the $1000 or so is a reasonable expense.