Download SX1 manual and you will know all.

I just bought SX1, Canon DCC-800 bag, 2GB SanDisk Extreme III, 8GB Kingston SDHC class 6, NiMH batteries.

SanDisk works great, Kingston is slower and if I take continuous superfine photos the buffer is full after ~10 shots and the speed drops.
Full HD video and continuous fine photos are ok even with the slower Kingston memory card.