First, the good:
There has been a conscious effort to tie this new series to the classic one, which ran on CBS from 1968 until 1980. For example, the opening credits were obviously created with the original series in mind, with fast cuts of the islands and the cast, high-tech graphics interspersed throughout, and a faithful updating of the series' theme (my favorite theme of all time). Interestingly, the revival's original theme was updated (with more brass) after the pilot episode to one which sounds closer to the original.
The writers have retained the same characters from the original series. Steve McGarrett, played by the stern Jack Lord in the original series and played here by Alex O'Laughlin (or AO'L as he is often called) is a Honolulu detective and former Navy man, whose father is abducted and then killed (maybe), prompting him to join a special governor's task force to fight organize crime on the islands. Danny Williams, originally played by James McArthur (Helen Hayes' son), is McGarrett's right-hand man and is played by Scott Caan. Special Detective Chin Ho Kelly (Kam Fong in the original) is portrayed here by Daniel Dae Kim (of LOST, also filmed in Hawaii). And Kono Kalakaua, played by Zulu in the first series, has been re-imagined into a female detective, Kona Kalakaua, played by Grace Park (BATTLESTAR GALACTICA revival).
And the writers have also tried to incorporate trademarks from the original show into this one. In the first episode we catch a glimpse of his father's garaged black 1968 Mercury, much like the one Jack Lord drove in the early years of the original series; sadly, we have yet to see the car on the road (I suppose it will somehow work into a future episode); the new McGarrett drives a silver 2010 Ford Mustang. Also, the catch-phrase "Book 'em, Danno," a phrase often repeated at the end of each episode of the original series, is still a work-in-progress here; the new McGarrett likes using the phrase, but the new Danny Williams doesn't. We know, of course, that if this show succeeds beyond the back nine episodes, "Book 'em, Danno" will become permanent.
Now, the bad:
The cast, though certainly attractive, exhibits a know-it-all snarkiness that gets annoying pretty quickly. Caan as Danny Williams can be especially grating in his acting style, especially when bantering back and forth with O'Laughlin as McGarrett. Also, the plots are paper-thin whodunits with unmemorable antagonists; so far there hasn't been a single villain with half of the chemistry of Wo Fat (Khigh Dhiegh in the original series). Additionally, the use of CGI (sometimes obviously so) to forward the plots becomes tedious and predictable. Finally, the fact that the task force has not yet decided on a name for their team seems contrived to build up to a climax in a later episode; so, should the show have no name until they decide that "Hawaii Five-O" would be a good moniker?
Ultimately, despite the fact that the producers and writers are laudably trying to appease fans of the old show, this new version will have to succeed on its own merits. Right now, that's a tall order.