Smart Media is being phased out, it's not terribly hard to find cards but many retailers will probably stop ordering more once their stocks are gone.  The memory controller is located in the reader so make sure the camera supports whatever size cards you are planning to buy, it's not like CF cards where you can use any size cards.  128MB is the limit so you might want to buy more than one card.  A better solution might be to get a xD->SM adapter, that way you can use xD cards which are easier to find and if you upgrade in the future you won't be stuck with completely outdated media.
But no, there's nothing inherently wrong with smartmedia.