Interesting, this happend to me too. I bought the 30Gb 3G-iPod, and one week _before_ it arrived, Apple launched the 40Gb-version.
The thing is, I thought I had a really weak case ("Hey, Apple, how about giving me a new 40Gb iPod in exchange for the 30Gb, although I have laser-engraved the old one? Because I want one, and it would be.... nice."). Thing is, AppleStore just said "sure, send in the old one and buy the new one already today, we will refund your money". I was so baffled I just sat there, staring at the phone, feeling the warmth spreading in me.
Now, offcource everything wasn't perfect at once, since AppleStore never gave me the refund until I wrote an article in MacWorld, and the 40Gb took two months to arrive. But anyway. It's worth a shot. At least one. At least, if you bought it from AppleStore.
Happy hunting!
/ Andreas
P.S. Just got that 40Gb iPod stolen last week. Can't say Im sorry, since the replacement (from the insurance company) is going to be a Photo iPod... he he... :-)
iPods 4G Anonymous