Sadly, the NX-01 design was lifted from the Akira class, Excelsior, and a few others. The designers of the NX-01 say they based in on the p-38 fighter. Yeah, sure.
There was a design similar, and a likely precursor to the 1701 of kirk, but Berman rejected saying Kirk's enterprise looked like a toy.
I've seen some nice fan made ones and even tried at making my own for a while.
http://www.spaceempires.org/gallery/fan/nx01a.gif
http://www.spaceempires.org/gallery/fan/nx01b.gif
Overall, I'm disappointed with Enterprise for the lack of original story telling. We've had what, 5 shuttle crash episodes in the first season, please, even voyager had less than that in the firt season.
The Temporal Cold War was actually another TV series that was going to be made by Braga, but paramount didn't pick up on it so they wrote it into Star Trek. They decided to toss it into Enterprise to silence the people that bash them for not being consistant.
Enterprise is the final deathblow for star trek. I am looking forward to seeing Star Trek Nemesis, but that will most likely be the end of my Trek days. Gene Roddenberry would change his name to Iben Scrood if he saw that [Enterprise] travesty....
In terms of mature, develoepd sci-fi, this is my ranking on a 1-10 scale. 10 is the most grown up.
Farscape : 10
Stargate SG1 : 10
Jerimiah : 8
Odyssey 5 : 9
Andromeda : 1
Enterprise : 2
Earth: Final conflict: 1
Voyager : 1
DS9 : 9
TNG : 9
TOS : 5