What is new in last 6 months? [ Since 3.30 ]

Already discussed: Version scan
Major service/os fingerprint update in 3.50, released Jan 21
OS Classification (vendor, OS, OS generation, device type)
Nsock parallel socket library, LibPCRE
Improved Mac OS X, and Windows support
Major NmapFE improvements (Peter Marschall)
Compact/cleaner output (NmapOutputTable class)

More details: http://www.insecure.org/nmap/nmap_changelog.html