When I first saw Enterprise, the ship seemed a bit too advanced for it's era in many respects. However it did have the "primative" feel, such as grappling hook (instead of tractor beam), an experimental transporter, spatial torpedoes, pulse cannons etc.
With the hindsight of the new Star Trek movie, the state of advancement for the NX-01 could easily be rectified if you go by the idea that the NX-01, the USS Kelvin incident, and the "Super Enterprise" of the new movie, all exist within the same alternate reality, starting with the destruction of the Borg sphere above Earth in First Contact.
Cochrane knew about the Enterprise (and thus likely influenced the naming of the first Warp 5 ship), the knowledge that there existed vastly superior races out there (the Borg) etc.
To our knowledge, a blackhole is a 1-way anomaly. However, within Star Trek we've never actually seen proof of what happens if a ship gets pulled into a blackhole. We've never seen "the other side". Until now. It could be argued that both the Narada and the Jellyfish possessed sufficiently advanced shielding to protect from the gravitational forces inside the black hole and thus got through to the other side intact. Perhaps the timeline was already an "alternate reality" before Nero arrived in the past, simply by continuing the timeline estabilished in ENTERPRISE.
All these facts together, and it would be very easy to explain both the NX-01 and the Super Enterprise superior technology compared to the counterparts of the "Prime Universe".
In conclusion: With hindsight, ENTERPRISE was a pretty good show. Particularly the 4th season which tried to rectify alot of the inconsistencies to match up with TOS. With all past incarnations of Trek, starting with TNG, DS9 and later VOY, they all started out pretty "slow" at first, and only reached their prime near the 3rd-4th seasons. With TNG it was Best of Both Worlds (3x26-4x01), DS9 it was Way of the Warrior (4x01-4x02) and VOY Scorpion (3x26-4x01). ENT did exactly the same thing by improving near the end of the Xindi arc, and the Storm Front 2-parter.
If you go into watching ENTERPRISE, expecting to see a ship more primative and dare I say it "cheesier" than the TOS Enterprise, youre about to be disappointed. Keep an open mind, and value it for what its worth: Entertainment. There are plenty of good episodes throughout ENTERPRISE if youre willing to keep an open mind.