This article is from the FAQ, by with numerous contributions by others.
Yes. You get 36 months of practical training (instead of 12 months
for an F1). Also, your spouse may work on a J2 visa during your
stay after getting permission from INS.
Is the J-2 visa holder (spouse and children of a J-1 visa holder)
subject to the 2-year home residency requirement, too?
I am a graduate student on J-1 visa. Do I need to have a secured job
in USA in order to apply for a waiver?
What is the USIA policy regarding approval of J-1 extensions while
a waiver of HRR request is pending?
As of September 1996 this is the USIA policy. USIA has stated that
extensions may be allowed for waiver applicants
BUT once USIA has issued a favorable recommendation for waiver (to INS),
an extension will no longer be possible.