Here is a link to my December 2017 blog post on AccountingWeb.com where I share my thoughts on the new Online Bill Pay feature in QBO, powered by Bill.com. It has some pros and cons, so weigh them all as you make your decision on whether or not to implement the add-on.
Here is the manual link:
https://www.accountingweb.com/community/blogs/jlinick/thoughts-on-online-bill-pay-for-quickbooks-online