The promotion goes all month but the extra $150 off ended on 4/4.
Most RC promotions are worth 25% or 30% off of the list price.
This promotion depends on the length of the cruise. For example a 6 night cruise would get a 33% discount (2 out of 6 nights free) while a 7 night cruise gets a 28.6% discount (2 of 7 nights free).
33% discount is very good, 28.6% discount is good but not the best.