I have a 128Mb+save. So far I have found no use for the save function at all. It doesn't seem to be compatible with the Tennokoe and it does not replace the Backup RAM. I've not had any luck writing homebrew code that saves to the Neo Flash save RAM either (surely it's possible, though). I wonder what the Neo Team was thinking when they added that feature
The Neo Flash is a nice thing to have, though. It's not nearly as user-friendly as R4 and the like, but with a bit of tinkering most (maybe all?) games can be made to work well. It still has some quirks that I don't understand, but it's good to be able to play homebrew and translations and hu-cards that I'll probably never find or be able to afford (Magical Chase).
If anyone is on the fence about joining a group buy and has some questions about the cart, feel free to ask.
HercTNT- mine came with a linker. I don't know if they can be bought without one. The Neo Flash card actually has pins on both sides--one side has a PCE/TG16 connector and the other has a GBA one. When you want to play, you plug the PCE side into your console and go to town. When you want to flash some new stuff on it, you plug the GBA side into the USB linker and run their flashing software.