The more annoying thing is when I wait nearly a week with no notice and no shipping update on the tracking number they generated.
What happens if you look up the tracking number? Do you see the package in transit?
If the seller generates a label and then just sits on the package for a week when they said 2-3 days, then yeah... that's just bad selling. I wouldn't feel justified leaving negative feedback just for that unless it went to crazy extremes, but probably some others would. But I'd certainly dock them on the star ratings for timely shipping - those star ratings do matter for prioritizing search results and seller fee discounts.
If the package is in transit, but you're not getting updates, then it's a matter of the seller not using their tools effectively. There are several ways to enter shipping information in eBay for sellers, and the buyer may not get updates depending on how the seller does it. For example, if the seller simply takes the package to the PO, jots down the tracking number, and enters it directly on their selling screen, you won't get any updates. eBay makes it relatively easy to do everything electronically, but not every seller wants to do it that way for various reasons (you at least need a postal scale at home, for example).
