I didn't really use Adobe stock photos before now, I pretty much used Getty and a couple alternates when I couldn't find what I need on Getty, and that was it. I somehow felt like I would not get as good a deal if I didn't go through the manufacturer.
However, over the past year or two, I've seen a lot of excellent new royalty-free stock photography houses blossoming. There's the trend towards all-you-can-download pricing (Shutterstock, LiquidLibrary), and the super-inexpensive, community-based sites (iStockPhoto). These have turned out to be a real boon for me when I needed simple, generic images. Need a picture of a plain old book? Or just a smiling dude? You'll find hundreds.
But when it comes to a large campaign with a 15000-piece print run, maybe you want something more unique. In those cases, I've moved away from the majors (Getty and Corbis) because they are not only expensive, but they are so popular there is a good chance that someone else will have used your image. Veer and Creatas are popular with a lot of designers, and they do tend to carry more unique images, but with a smaller selection.
After awhile, all this searching among several sites gets tedious. And some stock websites are considerably better than others - pricing at your fingertips, convenient comps and zoomed views, as well as how painful it is to page through 1100 images...the amenities vary widely from site to site. I find myself sometimes wishing one site had the xyz feature of another.
Enter Adobe Stock Photos. A convenient, robust, fast and slick interface that brings together the selection of dozens of stock houses, with fairly consistent and reasonable pricing. The only other thing I can ask for would be the ability to search for disks of images, or find the disk associated with an image if available (if I find one I really like, chances are there are others from the same photographer or shoot). And perhaps some additional "smart" search tools, but really when the interface works this well I don't mind looking through a few more images. I just bought my first three photos there, and I'm really pleased!