It's gambling. You can't say "it works" or "it doesn't work". To some extent, it does work, just like betting all your life savings on a 50% roll might also work, and it might fail. What you can say for sure however, is that it's not guaranteed to make you a profit.
However, you can make the probability that you will make a profit as high as you want -- 99.9% if you like. The tradeoff is that the profit you will make will be very small relative to the amount you will lose in that 0.1% case. (This is true even if the house imposes relatively low limits. You just need to make some small tweaks to the system. However, it will mean that you may need to play for a *very* long time.)Not only that. The chance of hitting your profit target (say, 20% or 100% profit) is indeed lower with martingale.
You can find a very long discussion on this in the thread https://bitcointalksearch.org/topic/does-martingale-really-works-610339.
