yea i own one
1. Do you use the GBA to browse your computer?
Nope... it comes with software which u can drag & drop ur gba roms into and click "write flash"
2. How well does it work?
All it does is transfer a ROM to the flash cartridge, then the flash cartridge emulates a GBA cartridge (also can store more than 1 game

)
3. Does it use .sav format for game saves?
Dont think so sorry
4. Can I use .sav files from Visual Boy Advance?
u could, but i doubt they'd work.
If u are gunna get a flash cart get a 128Mbit+ else theres no point (one a 128 u can store 2 big games, or 4 small ones)
I got a 128 cuz it was fairly cheap
Stez