[HarryT]

Yes, it will be absolutely identical to a non-ad version. In fact it will become a non-ad version. There is no hardware or firmware difference between a Kindle with and without ads. The ads will never reappear unless you re-enable them (which you can do at any time from the "Manage Your Kindle" page).

EDIT: Note that the "Reading recommendations" on the home page are nothing to do with ads. You turn those on and off via the "Settings" menu on the Kindle itself (Settings, Device Options, Personalise Your Kindle).