Confused about microSD speeds and their effect

Hi

I have a supercard lite and a 512mb san disk microSD and have read this link

http://forums.maxconsole.net/showthread.php?t=25505

Where they talk down the device although it’s been great so far, before I buy another microSD card I want to make sure I'm getting the best performance.

How does one run the Castlevania test? I've read that it’s the intro movie however when I run it, it goes straight into game play.

I've tried animal crossing and it seemed fine. The only stuttering I've had is when I move the menus around whilst an mp3 is playing in moonshell which obviously inst a problem.

Thanks in advance