Inpaint [the app] is remarkably simple -- one file & one necessary registry key [storing your registration/activation key]. I've found that the keys we get via GOTD are either the same or still work for older versions, so saving the old version just in case is a piece of cake, e.g. add a folder named Old to the Inpaint folder, & move it there. I can't think of one reason not to grab it when it's available on GOTD.
Google/Bing on Inpainting for all sorts of references, the theories behind it etc. In a nutshell it's a method of analyzing an image & stretching that image data. Ah, but you can easily resize any image you say... the trick here is that visually things don't appear to be stretched. In order for that to happen, Inpainting recognizes objects in the photo that can't be stretched themselves -- that way aunt Tilly doesn't look like her reflection in a funhouse mirror. And if Inpainting can recognize objects, the next logical step [which happened almost as soon as the 1st Inpainting app was released], was making it possible to remove those objects. Thus we have today's GOTD, Inpaint.
Now, why was that necessary when most people downloading GOTD apps know about Inpaint by now? I think it might make it easier to understand when Inpainting is the right tool for the job. The key is in the stretching part -- there are things in the world that can't easily be stretched, or painted with a clone tool/brush when they appear in an image. If you think that you can quickly & easily use a clone tool/brush with grass, then your standards &/or eyes are less than mine. Or try to match the pattern of bricks on a building or house. The key is whenever something is visually ordered & arranged, like individual blades of grass, or the regular pattern of bricks, which are also irregular on their surface & in the mortar between them.
It is possible to copy/paste portions of a photo to match something like bricks or stones, and you can clone grass using a brush to paint it in, perhaps only using the color & texture as the source of your clone, but fast & easy it is not. Likewise you can do vanity editing manually, enhancing someone's figure as they do on so many magazine covers, but filling in any blank spots [where the subject's body used to be in the image] can be rather tedious... copy a portion of or the person's full body, use Inpainting to fill the areas necessary, then paste their body back into place, touching up if & as needed.
Now Inpainting, like anything else you can do to an image or photo, has its limits. It can get confused by multiple patterns with well defined edges. Today's GOTD, Inpaint, lets you use guides & such to better define what gets stretched & what does not, but there are times when fussing with that sort of thing consumes any time that you'd save using Inpainting to start with. In those & many other cases it pays to think of Inpainting, using Inpaint itself or your editing app's built-in Inpainting tool, as just one of many tools in your toolbox.
One thing I'm trying to do is address many of the complaints I've seen posted when Inpaint or similar is offered. No matter how good or bad the implementation of the original theories that led to Inpaint, Inpainting tools & apps all have limitations that spring from that original theory itself. Simply put, regardless how it seems to some people, it's not magic. And on top of those limitations that exist with Inpainting in general, Inpaint, like any app you'll ever find, has it's pluses & minuses. That's why you have more than one tool in your toolbox.
You can use Inpaint on its own, or as part of rather than the entire process. Personally I don't believe there's a photo that you can't improve in an image editing app. OTOH, & practically speaking, if you were to give every photo the full treatment possible, you won't have all that many photos. So what the pros & semi pros do is some minimal editing, often en masse in something like Lightroom, then pick & choose a few to do more work on. Everyone can do the same sort of thing, if they want -- there are no rules on how much initial editing or adjusting you have to do, and nothing saying that you have to do any editing at all. If you feel that all you want to do is use Inpaint to take something out of an image, with no further editing needed, that's perfectly all right.
Image editing is best done by looking at your photo, deciding what you want to do, then dividing that into steps. If you come to an area you need to work on, it's often appropriate to select it, so that what you do there doesn't effect everything else. At that point [with the area selected] you can use whatever tools, including Inpainting, along with Undo to work your magic. If you want to use Inpaint [the separate app], turn your selection into a separate image, use Inpaint, then re-import it into your editor, pasting it in place. Or you might use a copy of the image in Inpaint, import that into your editing software, & if appropriate, select the area you want/need, & copy paste that into place on a copy of the original image.