The only non-official memory card i own was a limited edition 1 meg 'Driver' card. Various saves of the game were already on each slot and given it was less than half the price of a normal 1 meg card and looked funky - i thought i'd give it a whirl. I got rid of all but one saves and used it as a normal memory card.

All the time i used it i never had any problems with it, but when i decided to go retro on my PS2 and need a save from it - the PS2 would not even acknowledge its existence. Luckily i still have my PSX knocking about, so there wasn't a problem.

If ya want reliability and consistency - the official stuff is the only way to go.