With the additions of services like 500px, many have predicted the demise of Flickr. Yet it is still here. And it has received more attention in terms of development and design in the last couple of years than the five previous. I'd suggest that the Yahoo leadership has some sort of vision for the service and community … finally!
The recent new redesign of the service, as well as a great iOS app, has people reconsidering it once again. I've never used it as a primary backup location for my photos (I have a Dropbox Pro account for that), but there is another usage for Flickr. It has been my go to resource for photos when I'm working on site designs. Stock photography if you will. Even when it was languishing in its aging 2004 skin, it was still more useful in this capacity than many other services.
Here's why I like it:
Effective advanced search
Some sites have search functionality that boggles rather than enables. Not so with Flickr. The various options work as you expect, making it easier to narrow down the items you have to look through to get what you need.
Creative Commons licensing
One of the advanced search options is in regards to licensing. This ensures I can search for items that I can actually use in a project.
Of course, Flickr has long had the All Sizes link when viewing a photo. But unlike crappy stock photography site, photographers on Flickr often include the larger, original resolutions of an image. This means you have more control for cropping or resizing an image to use on your site or project.
The recent changes to the web version of the service are enjoyable. Browsing through a photostream is a pleasure, and reviewing search results is greatly improved by the larger images and layout. The previous versions had smaller thumbnails in a rigid grid — I find the new design much improved.
Closing: Even with many new services available, I still turn to Flickr when I need an image for a site design. The new design only improves its usefulness in this regard.