There's a lot of improved file-system support that's been worked on for ReactOS 0.4.2, including read support for ReiserFS and UFS/FFS along with read/write support for both EXT3 and Btrfs. ReactOS 0.4.2 also features Cygwin support and .NET 2.0 application support. ReactOS support has improved to the point that games like Elder Scrolls: Skyrim and Doom 3 should even be playable on this "open-source Windows" OS.
Those curious about some of the applications/games working on ReactOS 0.4.2 can be found via this Wiki page.
If you are interested in helping test this near final version of ReactOS 0.4.2, visit SourceForge.net for downloads.