the good trader never skip demo trading , they practice always besides a real account . they practcie any kind of new trading strategy on there to see the performance how it works.
trading in a demo account is more appropriate for beginners level and besides this to finish psychology of schhol from baby pips is really important , its a very good combination for learning as new forex trader.
there is no trading strategy whcih work for a long time , its all about short time trading approach even in spite of having most powerful money management.
customer support is really important , i agree . but the more important is when time to withdrawal , generally the good broker never long traders withdrawal.
i dont know honestly what percentage are failures but i know most of them are failures especially the traders who are newcomers. there is nothing 100% in Forex trading.
the demo is really important but i have seen the knowledge we get from demo account actually not works in a real account, its real psychology. we cant focus when trading in a demo.