It's only applicable to those folks who have been on H1B over 6 years OR have an approved I-140.
For those who don't know, employment based green card has three stages
1. Labor Certification (PERM)
2. Immigrant Petition for Alien Worker - I-140 - This stage checks whether the company filing your petition is legitimate and there is no fraud.
3. Application to register permanent residence - I-485. This stage checks whether the person applying has a good character, is not criminal etc. etc.
Getting through 1st and 2nd stage takes 1 to 3 years. It's the 3rd stage which has a long wait, mainly for people from India or China.
See: http://travel.state.gov/content/visas/english/law-and-policy...
As per that link, USCIS is processing cases of folks who applied in 2007 (for EB2) and 2004 (for EB3).
This is definitely a huge relief for those folks who have decided to apply for permanent residency and have been stuck in stage 3 for many years.
P.S.: I know about this because I am from India and went through a grueling 10 year immigration process to get my green card.