I made this pallet picnic table just before Summer as I have visions of sitting out by my lemon tree drinking some beers with friends in the warm sun. It took roughly 4 hours to complete from scratch with no sanding or preparation of the wood (as it would be outdoors, I may paint it some day).
My advice for anyone attempting a build like this is to work on it from side-to-side. By working in such a manner, you can quickly work on the piece while it's on the floor (i.e., put the legs on one side, flip it over then place the legs on the other side) as it's easier to put hammer/screw from the top down.
The top part is just a single pallet, unaltered. Legs are hardwood so are very stable and robust. The seat isn't the best, in future I'd recommend making it at least twice the size as it puts a lot of pressure on a small part of your behind.
I look forward to seeing your design!