Is polymeric sand necessary for paver joint

I just completed a 90 square foot patio. I ended up putting down 4 inches of paver base (crushed concrete), 1 inch of sand, and then the 2 inch patio stones... so I dug down 7 inches all around. To be honest though, I went deeper than that in some places and ended up having to bring in much more paver base (crushed concrete) than I really needed. So maybe I have 6 inches of paver base in some areas. In my opinion, the key was the compacting. I highly recommend you rent a plate compactor. You should be able to rent one for less than $100 for 4 hours and it is completely worth it. You will only use it for 30 minutes but it will make the crushed concrete as solid as rock.

Also one of my neighbors who is a landscaper joked about how far I had dug down... he said I went way too deep and now I can land a helicopter on my new patio. I tend to agree with him that the 4+ inches of paver base was more than needed but still I am happy with how it all turned out.

Couple other notes:

• After compacting the crushed concrete it was smooth and solid. When you walked on it nothing moved... kind of like walking on concrete.
• Lowes/Home Depot sell paver base by the bag but that is much more expensive than having it delivered. 2 tons (approximately 1 cubic yard) of crushed concrete was not enough to cover my 90 square feet to a depth of 4 inches; I probably ended up putting down 3 tons.
• Since the patio was positioned next to a concrete sidewalk, I used an 8' 2x4 with a piece of scrap wood nailed to one end which gave me a depth of 3 inches (the sand and paver depth). Then I pulled the 2x4 back and forth across the area (with another person holding one end on the sidewalk) to level out the paver base before compacting (and to know where the shallow/deep spots were).
• I used 1 inch diameter pipes to give me the 1-inch depth for the leveling sand. Put two pipes down on the compacted paver base parallel to each other and then pour the sand on top. Then pull a 2x4 over the pipes to level the sand. Remove the pipes and then fill in the indentation by hand. Now lay your pavers (or patio stones).
• I used polymeric sand to fill the cracks in between the individual patio stones.

Updated with photo for @Chris Marasti-Georg (2013-05-20):

• Dig down at least 6".
• Lay landscape fabric (this will block weeds and what-not), the fabric should run up the sides of the hole.
• Fill the hole with a base material (usually crushed limestone), fill the hole about 2" at a time tamping it down thoroughly between layers.
• Add a 1" layer of sand (leveled).
• Set the pavers.
• Brush sand into the joints, using a stiff bristled broom.
• Tamp the whole thing (this will wiggle the sand between the pavers locking them in place).

You may have to dig deeper depending on where you want the pavers to sit (at ground level, slightly above ground level), and how thick the pavers are. You'll want 5-6" of the base material, plus 1" of sand, plus the paver thickness (keep in mind the 1" of sand may compact a bit when you set the pavers, and after the final tamp).

To make the job easier, you might want to rent a Plate Compactor this will make tamping the base material easier and help lock in the pavers after you sweep the sand in the joints.

Typically when you build this type of "patio" you'll have to worry about drainage, so you'll want to slope the whole thing enough to allow the water to run to a safe location. In this case you probably won't have to worry so much, unless the patio is right up against the house.