The Pico Dolly is pretty awesome . Sure you can probably DIY yourself something that functions similarly but I find tremendous value in the included flexible arm and universal shoe-to-tripod mount. The case is also convenient to have. The flexible arm does support the weight of a DSLR such as the a77 with 16-50 SSM lens but it does not inspire confidence and requires experimenting positions to get it to balance. Adjusting the wheels is fast and build quality is high.
In order to mount standard tripod heads a 1/4″ to 3/8″ adapter is required. You can find that here.
The dolly requires an extremely flat surface. In the following test you can see how some wooden tabletops create a less than smooth shot. This thing allows you you to be creative with your shots and gives you options beyond a standard slider.