One thing that has been mostly under the radar so far is that it gets the final say on the agreement assuming the UK Parliament accepts it. Although they can't make changes, they can block the agreement if they do not like the proposed implementation by the UK.

Right now, there are decided rumblings. E.g. the UK promised an independent body to safeguard the rights of current EU ex-pats but that body is now shaping up to be a subsidiary of the Home Office.