GKE hit on a very important point. If this allegedly hostile planet had planned to wipe out Earth, they would hardly send a 'test probe', with one of their own on board, to alert Earth to the danger. I think it far more likely, as Recoil suggests, that the Shadow Futureman is setting Earth up. He may well be trying to get Earth to wipe out a future enemy of his. His motives are currently unknowable, but they do seem complex. I like that part. Trip's blatant hatred for this unknown and unseen race, due to the supposed death of his sister, looks like we/he are being set up to find out things aren't what we were told.
While I don't object to the Enterprise wiping out Durass's ship, until that happened, I expected the Klingons to show up much later, next season, with them and the Enterprise becoming allies of necessity to survive this strange area of space, where the laws of physics don't always apply.
I am also of the opinion that the Vulcans are sort of mentoring us while we do it on our own, and graduate to being allowed out in the galaxy without supervision. Seems to me that there is some brief mention along those lines in First Contact. It is more improbable, and harder to see why we go along with it though.
As to humans catching up with more advanced races in 100 years, I don't think that is so improbable. Look at the huge scientific advances we have made in the last onehundred years, from the Wright Brothers to the Space Shuttle. BUT -- in TOS, I don't think the humans were on top technologically, by any means. Humans could play with the others, were roughly equal to the Klingons, but seemed out matched technologically by the Romulans, and many other races that were always snatching the Enterprise for one reason or another.
On the whole, I don't think Enterprise has been great, but compared to most TV, not that bad either, although some eps are uninspired to say the least. B&B seem to be trying to lay the groundwork for some strange departures from the norm, and I find that good and hopeful, but I guess I am as skeptical as most here as to whether they will actually pull it off well.