Brakken has done a quality review of the new M3 Lite Flash Cart for the DS, heres an excerpt:
Welcome to another review of the M3 Team’s excellent line of Nintendo DS Multimedia, Development and Backup units the M3 Perfect Lite. Ever since the early days of it’s conception the M3 Perfect has boasted very great compatibility with homebrew and receives constant support from it’s creators when it comes to updates enabling it to run mostly all the backups you could ever make.
Not much has changed in their Nintendo DS Lite only version – the M3 Perfect Lite – other then its physical size. It’s now almost exactly the same size as the filler cartridge that comes with the Lite. It fits flush inside the console without sticking out a bit. Additionally, it comes with two different color casings that you can use leaving you with a cartridge that matches your console in not only size, but now looks.