AFAIK the copyright notice is valid, but only applies to the page and line layout plus cover layout of the new paper edition, not the PG text. Not that they would tell you that.
Not in our opinion (which has been vetted by several expert copyright lawyers):
No Sweat of the Brow Copyright http://www.gutenberg.org/howto/sweat-no-c
Not sure about in the US, but the case law, at least when I researched it about 7 or 8 years ago, was still unsettled in Canada and other commonwealth countries. I don't know off hand that that situation has changed. In the UK, most if not all EU countries, and much of the Commonwealth - - though not in Canada -- there is also an express provision protecting "editions" or "typographical arrangements". The term is generally shorter than full copyright, and of course they aren't exclusive. You can prepare another edition or typographical arrangement of Shakespeare in the UK, you just can't republish an exact copy of someone else's in the first 25 years after publication. Quaere; does "edition" or "typographical arrangement" copyright subsist in PG e-texts, in countries which recognize those types of copyright?