As much as I love the iPod, the earbud covers suck. I put a new pair on yesterday, and they've already come off.
And it seems to be impossible to buy earbud covers. You'd think they'd be available at Fry's in packs of 500, but no....
Update, 25 June 2005: It's only taken me six months to get to a Radio Shack-- one I stumbled upon while on vacation in Southern California, no less-- and buy a set of replacement covers.
So far, so good. They're thicker foam than the original iPod earbud covers, but don't seem to affect the sound. My one complaint is that at $3 for four, they're a bit pricey. However, I have the satisfaction of knowing that I'm going to help the thousands of people who hit this post every month. or at least satisfy their curiosity. if they're in a country that has Radio Shack.
Update, 24 August 2005: LavaLady reports out that Apple now sells replacement earbud covers. (Search under "earpad," a totally non-obvious term IMHO.)
Update, 17 September 2005: Lifehacker recommends the earPod travel case for the iPod headphones, and the Sumajin replacement earbuds. I saw the Sujamin earbuds in the Apple store recently, and they're pretty cool. I've never seen the earPod, but I've already found the perfect earbud carrying case: Sony makes it, and they come with their lower-end headphones-- the ones that cost either $10 (e.g., the MDR-E828LP Fontopia) or $15 (e.g., the MDRE821V) at Fry's. Since the earPod costs $10, I recommend getting a set of the cheap Sony headphones: you'll have a carrying case, and a backup set of earbuds should you lose your main pair. Of all the products Sony makes, I think their round, winding earbud case may be the most perfect: it does what it's supposed to do absolutely brilliantly.