I have seen some comments that it is required, some that it is best practices.
Has anyone experience with runing SharePoint in a load balanced environment without sticky IP.
Yes you need to run sticky sessions when running SharePoint and NLB to ensure that the provisioning process works. For example creating a publishing page first triggers an item created for the file, then an item update for the meta data being added.
Even without NLB you are almost always required to run sticky sessions if you have more than one WFE. For example depending on authentication method you will also be prompted again, if your second request were to be sent to another WFE.
hth Anders Rask