How secure are Hardlocks/ Dongles really??

[G-Dorion]

Hey folks,
I gotta develope some schoolwork about Hardlock or dongles, mainly USB, for a computer science course.
So I did some research on the web n I read everywhere that those USB-keys are really secure and cannot possibly be cracked. So that there is no way to bypass or copy them.
Now I'd like some info from the "other side".
What do you know about them? Has anyone ever tried on one of those?? U ever heard of anything, or anyone who tried succesfully or not???
Really any Information could be useful.
Thank u very much

G-Dorion