The 1Mobile Market for Android offers a curated selection of fun, useful, and otherwise interesting apps, all of which are free. It's unique because it's managed by a team of actual editors, rather than a set of algorithms that try to home in on what you're looking for.
First thing you'll notice is that 1Mobile's main panel looks a bit like a cheap knock-off of Google Play, with its large tiles and similar color scheme. For some, this might be comforting, but for me, it feels a little tacky.
While looks may not be 1Mobile's strong suit, the app does offer tons of value in other ways. It's a lot more manageable (size-wise) than Google Play, and it offers a number of useful tools to find the apps you're looking for.
Swipe left from the main panel, and you'll see a list of categories for a typical browsing experience. Swipe right to see Top apps, AppLists, and Editor's Picks. AppLists are uniquely helpful, in that they group apps based on specific interests. For instance, there are lists for Fitness fiends, vegetarians, movie lovers, bookworms, and so on. These groupings are one good reason to check 1Mobile before going straight to Google Play.
Another way to find apps on 1Mobile Market is through Search. If you do a typical keyword search, 1Mobile will attempt to autocomplete your terms, which can be very helpful. Also, there's a unique (thought not necessarily useful) keyword cloud that offers handfuls of typical search terms for you to try.
It's important to note that you don't actually download any apps directly from 1Mobile. Rather, each product page just features a link, which leads directly to the download page on Google Play. Also, on the product page you can Like or Dislike an app, see all its vitals, and view screenshots.
One thing to watch out for with 1Mobile is invalid links. Since the whole market is curated by editors, sometimes a recommendation can lead to a page that no longer exists on Google Play. This happened to me when I came across a recommendation for the classic NES game Contra. Seeing a link to one of my all-time favorite shoot-'em-up games got my hopes high, but clicking through to a nonexistent download page quickly grounded them. The game was no doubt pulled for copyright infringement issues, but 1Mobile's editors had yet to update their database.
Overall, I think 1Mobile Market is an outstanding tool for sifting through what might otherwise be an overwhelming Google Play store. It offered me a lot of great recommendations for apps that I likely wouldn't have found otherwise.