so far the card has worked very well....haven't tested extensively because i got mario kart today as well, so i've been playing some regular cups and online.
but ds games load almost instantaneously...no wait time really with the cf card i got. i also haven't experienced any slowdown either in the fmv type sequence in castlevania people have reported.
i have only used the faster load setting -dma 4x i think its called- which means instead of loading data into the m3 ram then to ds, it loads straight from cf to ds...this is not supported on all cf cards...most games seem to work with the fast load method for me(i havent tried the normal method). i ordered a 1GByte corsair card off newegg for about $50.
i'll post some pictures soon...also i tried converting a captured video into gba format with the free convert software included....worked decently at standard setting, 42 megabytes for a half hour show...sound could have been better...but again i tried only the standard settings, with tweaking the video can be made cleaner im sure. good enough for a quick train ride or something.
one other thing i tried putting a gba game on the card...it didn't want to run. even weirder is when i stuck the m3 in the gba it loaded the gba games up fine....gotta look into it.