Most traders use leveraged accounts, percentage gain is meaning less. % gain is for investors who park their money somewhere and hope desperately. Not for traders who want to make a living. Ever heard of the ratios of cagr, omega, sterling...
the best quote i heard from someone about sim/demo trading was that 'you'd do things sim trading you'd never do real trading', and i agree with munnyhunny's '100%', done it lots of times myself, as well as resetting the sim account after blowing it what i recommend even tho you may be suspicious of fx brokers is to open a micro account with an fx broker of your choice eg FXCM's: http://www.forexmicrolot.com/ minimum $25 - most fx brokers offer micros, also Oanda: http://fxtrade.oanda.com/ where you can open an account with $1 whatever your trading system is it will for the most part also work trading fx pairs assuming it's a straight buy/sell system while demo/sim trading has its uses, there is no question trading with real money is a totally different animal, or rather, you'll discover your self's real trading ability and most importantly, your reaction to LOSS - losing Your Real money sim trading is shadow boxing, real trading is getting in the ring with an opponent
I did not read the entire thread but I just HAVE to mention that even though it might be a good idea to test ideas in a demo account before going live, that I think it's essential that someone practices with at least a small amount of money. You cannot POSSIBLY gain real experience with demo trading.