How accurate is Ussher's OT and NT chronology?

[alec]

The Allan Longprimer bible includes a chronological date at the top of most pages in both the old and new testaments. According to the Note on the References (p7):

In the matter of chronology it is generally agreed, among conservatives as well as liberal scholars, that dates prior to about 2000 B.C. are unreliable and rather speculative. In this edition no dates are given before the twenty-first century B.C., but from that period onwards a system based largely on Ussher's chronology, with certain corrections, has been followed... While the accuracy of Ussher's measure is not guaranteed, it is reasonably correct and the notations will be useful to many.

Droll as the last statement in the quote may be, I for one have been thrilled with the inclusion of the dates. At times they seem to jump out at me, for example in Joshua 14.6ff when Caleb receives Hebron for an inheritance. Seeing this as the 13th century B.C. brings an immediacy that I hadn't previously experienced. It's not that long ago.

Apart from the Oxford comments above, what is the general consensus on Ussher's dating? Is it trustworthy?

Are dates before the 21st century B.C. speculative and unreliable? The Jewish calendar has no problem saying we are entering into the year 5774.

Your help is much appreciated. Forgive me if this is the wrong place to post this.
Alec

 

[Jerusalem Blade]

Hey Alec,

I have a lot of books I've collected on Biblical chronology, and myself I think the early dates are pretty accurate. Next time I see you I can lend you some if you want.

 

[GulfCoast Presbyterian]

Steve: Do you mean Ussher's early dates are accurate? Or those of some other chronology?

Thanks!
Mark