The Samsung Focus Flash is essentially a Focus S in a smaller package. It represents an excellent value (Free with two-year agreement) amongst AT&T WP7 phones and brings high-end performance to an entry-level device.
Of course the Flash does cut a few corners to keep its costs down. It features only 8GB of storage instead of 16GB, and the 5MP camera lacks many of the options found with the 8MP module on the Focus S.
The 1.4GHz processor is the same Snapdragon processor found in high-end WP7 phones.
Though on the smaller side, the display is still WVGA and Super AMOLED Plus which gives a crisp, vivid image.
It is compact yet manages to stay relatively feature packed. If cost is a concern, it's tough to argue with Free!
8GB of storage (with only 6.6GB user accessible) is a travesty that's made worse by the lack of an expandable storage slot.
Cellular signal strength appears slightly weaker than other smartphones.
HSPA+ 4G is underwhelming on AT&T's network and made worse by the fact that AT&T is switching to LTE.
The 5MP camera isn't exactly bad, but don't expect to be impressed.
If you absolutely have to have a WP7 phone, and it has to be free, the Focus Flash is the best AT&T has to offer. Just know that you'll be limited in storage space, and don't expect it to replace a real digital camera.
The Flash is also a great MP3 device, so long as you don't plan on carrying more than 6GB of music. It's not a great choice for video, though. There just isn't enough storage space for HD content, and you'd likely prefer a larger screen.
As great of a value as the Flash is, the Nokia Lumia 900 certainly challenges that spot. It costs a bit more, but doesn't cut any corners.