New from Tepples is an update to his speedtester for libfat app:

This program tests how fast data can be read from the CompactFlash or Secure Digital card inserted into a GBA or DS through an adapter. It works on any adapter supported by libfat, including those with GBA-compatible DLDI drivers.

2007-08-06: run all tests on one screen, use more precise timing, detect and report broken drivers
2007-08-05: DS support
2007-08-04: switch from gba_nds_fat to libfat
Download speed tester for libfat (99 KB; includes source code, GBA binary, DS binary, and required test file)