AppShopper has been a very good service (in the past, at least, I haven't paid much attention lately), with a variety of uses. One of the key ones for me was, I had marked "I own/have this" on a bunch of apps, and was subscribed to the RSS feed for updates to things I'd marked... you know that situation where you find an app that's almost what you want, but it's got a glaring deficiency or bug, so you take it off your phone? Oftentimes, a few months later, AppShopper would pop up with news of an update to said app, showing that the bug/deficiency was fixed, leading me to go back to try that app again. There was no other good central way to track such things. It has had other uses as well - a lot of people would throw apps that seemed kind of interesting on their wishlist, then buy them if/when they were informed that the price had dropped.
AppShopper and TouchArcade are part of the same company as MacRumors, as well, if I understand correctly, which is part of the reason why MacRumors has always listed their links in stories (next to a direct link to iTunes). Ah, I just noticed that the "Links" section at the bottom of every MacRumors page has gone from listing recent items from TouchArcade & AppShopper to listing recent items from TouchArcade and the YouTube MacRumors channel, as of sometime very recent - a reasonable change, since the "news" section at AppShopper was never kept up, it was still reporting on the "new iPhone 6s" just recently (I kept meaning to suggest to them that they change it to show the new apps feed from AppShopper instead of the news feed).