I am using 7%. In 2001 my FA used 12% in his projections, he changed to 10% in 2003 and then, at my demand, to 8% in 2005 (our portfolio was about 90% stocks back then). Looking forward, Morningstar projects annual returns of 5.5% for bonds, 7.6% for US large caps and about 8.2 to 8.4% for riskier stocks (small caps and foreign). Morningstar predicts a 7.5% return for my overall portfolio, so I use 7% to be on the conservative side.
But in my opinion, the returns projected by Morningstar for stocks (on a risk adjusted basis) make them a less compelling investment than in the past relative to bonds. That's why my portfolio is fairly conservative for someone my age (33, 65% stocks / 35% bonds and cash). I am just not sure that, going forward, taking more risk in the stock market will be rewarded accordingly. I might be wrong, but in the mean time I am very comfortable with that asset allocation.
But I noticed that a few financial gurus still use 10% annual returns, like Dave Ramsey on his new Fox Business show...