I guess I'm in a situation unique to most other posters here of having "come of age" during this "lost decade".
I have tracked investment returns and net worth changes quarterly for exactly 5 years as of January 1, 2010. The beginning of my tracking also corresponds closely to when I finished college and got a "real" full time permanent job (roughly 5 years ago).
The numbers are in, and I had an internal rate of return of roughly 3.8% per year in the portfolio. However continued inflows made the total value of the portfolio increase by a factor of roughly 1000% over the five year period. Net worth is also up by a similar magnitude. Partly that is due to starting off with a modest mid-five figure net worth and portfolio size. But it is also due to strength in income and growth of income over the years which allowed increasing savings and contributions each year.
So while I only saw a 3.8% internal rate of return over the last 5 years, my portfolio value and net worth grew by roughly 60% a year (on average). For my financial well-being, this was most certainly NOT a "lost decade".
Retired in 2013 at age 33. Keeping busy reading, blogging, relaxing, gaming, and enjoying the outdoors with my wife and 3 kids (4, 10, and 11).