I agree with the above posts. I bought a cheaper 4GB Transcend SD card and it had worked for months and months, before going on a photo shoot 4.5 hours away I purchased a sandisk extreme III. Long story short, when I needed it the most, the 4GB Sandisk failed me after taking a few photos with it. The good part is that I started with the extreme III card and then switched to the Transcend. Luckily I had my Macbook Pro there to dump photos on and continue using the 1GB card.
2 things to take away from this:
1. Don't put all your eggs in one basket, if I had loaded up 4GB of photos and then it crashed, well I would be one sad camper, and one less client. Having 4 quality 1GB cards would be ideal. (for my camera at least, a 21mp camera or shooting 10 fps would eat up a 1GB card, thus a 2 or 4gb would be a better choice)
2. I tried to save a few bucks on the Transcend card and it bit me hard. The money saved is nominal and now I have a $65 paperweight, that Transcend wont fix under warranty.
Also I always buy online, you can get things a lot cheaper that way. Everything at my camera shop is MSRP, I bought my D80 local to get the service. Also try out
www.newegg.com they have a bunch of deals on memory cards.