The drawback to Sony's MemoryStick format has been (1) higher prices than other memory card formats and (2) the 128MB upper limit to its capacity.
Last year Sony changed the technology to handle larger capacities, calling it MemoryStick Pro. Sometime soon this year, you'll be able to buy a 4GB version, should that be your need.
One thing Sony didn't change, though, was their higher pricing. The 4GB model is US$900 -- some 50% more expensive than the same capacity in CompactFlash format.