However, I find the interface gets pretty messy after a while. If you have several campaigns and you are constantly adding/deleting and trying new ads, your pages become cluttered up very quickly. Even if you click 'Hide everything I've deleted', it doesn't really hide it since it references to the 'deleted campaigns' or 'deleted ad groups' all over the place.
Am I missing something obvious? I e-mailed Google and they said that they kept all of your old data (even the deleted stuff) in your Adwords control panel for recordkeeping purposes. But I know there are many people who use Adwords Select far more than me, and they can't be dealing with this mess, surely?
Finding it less of a mess more of a use the expired data and ability to check back. I expect google need to keep it at least between invoices.
That said I have set up a couple of campaigns for one same site which were in competition competed with each other on the same terms languages and countries which in hindsight was not that clever and probably explains why one of them did so much better than the other .... :-)