Judy Novak (packetstan.com) used to offer a scapy class through SANS.

Oh yeah, you might also get some mileage out of nping (comes with NMAP and even works in windows unlike hping).  Very similar usage and flags, though not as flexible as scapy.

Packet crafting skills are not needed in the CISSP (at least it wasn't when I took it a few years ago).  However, they are very important for security.  You may not use it a lot, but if you can master packet crafting you obviously have a good understanding of TCP/IP.  That goes a long way in recon and identification and in some instances exploitation and covert communication.

IDS/IPS vendors will require a lot of packet crafting, firewall developers, network hardware vendors, any offensive security company...all of them will have a desire for packet analysis.

If I could do it all over again, I would have skipped college (BS and MS don't really contribute to the fun stuff) and the associated costs and really spent more time focusing on technique and studying the soft skills more (social engineering type stuff).