According to www.dapreview.com, the version sold at Walmart is the DAH-1500i - note the "i", it's important. It is a USB2.0 device (the standard one is 1.1) and also supports DRM (which the standard does not). It also sounds like the battery life is SHORTER than the base model.
MobiBlu at dapreview
There are now claims on www.dapreview.com that it is not really USB 2.0. Since it's only a 1G or 512M player, at least it won't take THAT long to fill the thing up.
By the way, www.dapreview.com is a very good place to go to keep up with all the strange (and not so strange) audio and media players out there (many of which do not make it to the US). They were "reporting" on the MobiBlu when it was only available from the manufacturer through ebay.