FAA has published a Q&A on this relatively new type of clearance associated with SIDs and STARs.
I wrote about these clearances when the “climb via” version was announced in 2012. Details here.
You can find additional information from NBAA here.
AOPA has a story about a report to the General Aviation Joint Steering Committee (GAJSC) concerning loss-of-control accidents. The detailed report is available at the preceding link.