The big highlights for this release is Haswell support along with its respective GPUs and OpenGL acceleration is enabled by default.
This is the first release that doesn’t have a 32-bit version. 32-bit i386 DragonFly BSD has now been abandoned by the project. With very little 32-bit hardware in the pipeline from vendors, there was no reason to continue with the significant support required to maintain an i386 version.
DragonFly BSD 4.0 brings support for 256 CPUs, up from 63 for SMP systems.
Network performance has been increased significantly especially around the UDP protocol. PF has been re-worked to now work concurrently over multiple CPUs.
What didn’t make 4.0 was HAMMER2 as critical components are still missing to make this next generation file system available to users. Matthew also stated that at this stage, users will not see it in 4.2 either.