More and more articles have been appearing on the EXT4 filesystem. In fact, the article that really caught my eye was one recently regarding the speed of using EXT4 on flash media. The benchmarks posted speeds of EXT4, showing it excelling over filesystems like FAT32 and NTFS by considerable amounts. As this article above states, many flash drives come with Microsoft's FAT32 which is nice because of compatibility. Most operating systems can read/write FAT32. But, Microsoft has recently started to bring up patent threats against the use of FAT32, which is one reason I have started to steer away from it. Also, it has a 2 GB limit on file sizes. Even though FAT32 is more compatible, I can see the benefits of using EXT4, especially on small and slower devices like flash media. Plus, as flash drives have become larger, the 2 GB limit of FAT32 will start to be more of a show stopper, especially when working with large video files, etc. And unfortunately, NTFS support is still scattered, because it is kept behind closed doors by Microsoft.
If you are mainly using Linux systems, I'd strongly recommend the EXT4 filesystem for disks as well as flash media anyway. It's been around for a while now, and it is considered stable. Even though the tests are showing microscopic differences in speed between EXT4 and other filesystems, there are added advantages of an efficient filesystem like EXT4 besides speed alone. Personally, getting rid of garbage filesystems like FAT32 or NTFS which are cluttered and need defragmenting, as well as being known for file corruption, is just one example. The EXT3/EXT4 filesystems are complete journalling filesystems, and do not need defragmenting utilities to be run on them like FAT32 and NTFS.
With Linux distributions (Fedora being one that boasts fast booting) reaching record boot speeds with each new release, I'd have to believe that EXT4 needs to take some of the credit. It's used by default with Fedora and other distributions now. Great stuff as usual here. Also, if you are really worried about compatibility with Windows systems, there are EXT4 filesystem drivers available for Windows.