The headline feature for 0.4.10 would have to be ReactOS' ability to now boot from a BTRFS formatted drive. The work enabling this was part of this year's Google Summer of Code with student developer Victor Perevertkin. While the actual filesystem driver itself is from the WinBtrfs project by Mark Harmstone, much of Victor's work was in filling out the bits and pieces of ReactOS that the driver expected to interact with. The filesystem stack in ReactOS is arguably one of the less mature components by simple dint of there being so few open source NT filesystem drivers to test against. Those that the project uses internally have all gone through enough iterations that gaps in ReactOS are worked around. WinBtrfs on the other hand came with no such baggage to its history and instead made full use of the documented NT filesystem driver API.
Seems like another solid release. While ReactOS always feels a bit like chasing an unobtainable goal, I'm still incredibly impressed by their work, and at this point, it does seem like it can serve quite a few basic needs through running actual Win32 applications.