OK, Be Careful of Risk!!!
Simple Math
For example: Assume you have $1000, ^DJI up 10% (in 1st wk), then down 10% (in 2nd wk)
If you buy DIA: 1st wk = $1100; 2nd wk = $1100 x 0.9 = $990
If you buy DDM: 1st wk = $1200; 2nd wk = $1200 x 0.8 = $960
If you buy DXD: 1st wk = $800; 2nd wk = $800 x 1.2 = $960
You can check DIA/DDM/DXD or QQQQ/QLD/QID of 2007 returns. It is NOT 2 x.
Point is that you can only use it for very short term (i.e. DT). No holding, otherwise you are the loser!
According to my understanding to the Fidelity Mutual Funds. The Returns should be already after fee/expense, and should include all the dividend/capital gains distributed. Attached Figure 1 is from Proshare Prospectus. However, you can see what actually happened in Attached Figure 2 (QQQQ/QLD, 2/28/07-2/28/08).