Sprint clarified that this is not supposed to replace Android Market, or offer only Sprint apps. It is actually supposed to ease the transition to a smartphone with Android for first-timers, who have a hard time sifting through the 80 000+ applications on Android Market to tailor their phone to their own preferences. Not a bad idea, considering that you can also get a shell ID, and start populating it with your own stuff from scratch, then erase it and start anew.
Switching IDs takes about 20 seconds, and downloading them about a minute or two. The nicest part is that Sprint ID will be open for developers to create their own concoctions and upload them in the database. Have a look at a video preview of Sprint ID in action below.