Dave is correct. Major SILVAR (Silicon Valley Association of Realtors) like to use these forms, and it is interesting to see comments in the MLS periodically from agents requesting "PRDS forms please."
I like to use these forms as they are very pro-buyer, and there is less opportunity for error (look at all of the different checkboxes on the CAR contract, I see too many agents make mistakes). They also incorporate "As-Is" language into the contract very nicely.
One of the disadvantages that I have seen, though, is that the seller has the option to cancel the purchase agreement if the buyer is late on one of their contingency removals.
The nice thing about the CAR (California Association of Realtors) agreements is that the seller at least has to provide a "Notice to Perform" to the buyer before cancelling.
Of course, we highly avoid trying to get into those situations. :) Just noting some differences I have seen.
-Aaron Wheeler, President, Oakville Properties & Oakville Capital