Having the game to pause while you're pressing the save state button is both annoying, but also having it directly written to the SD everytime isn't great for the SD.
So I have a suggestion, why not write the save state file to /tmp (or even just keep in the programs memory), and actually write to the SD when /dev/batt would reach a certain level (which at the same time would discreetly notify you of the low level of the battery, as hardly anyone ever gets to see the red LED when it turns on), or when you'd load a new game or exit the app.
The change would be transparent to the user, unless he decides to switch off the gp2x straight, and save/load state would be pretty much instantaneous and would do without a write (or even read) to the SD. What do you guys think about that?
EDIT : In case of a crash or anything I thought that the save state could be silently backed up to the SD regularly, by silently I mean writen very slowly to the SD so that it doesn't affect the performance, dunno if it's possible, I guess it should be