Here is my brief review of Safedice.
I deposited 0.01 BTC
autoroll until balance = 0.012BTC
deposit is not instant (because of bitcoin), but withdraw is instant.

With 50% win chance, and after auto rolling 1-2 hours,
my longest losing (and winning) streaks were approximately 8 dice rolls.  

The supported languages are: English, Chinese, Russian
There is live chat (in English).  In chat, players discuss their betting strategies and wins/losses.  Very interesting to read.

Update1: I just re-deposited another 0.01 BTC.  Now seeing streaks of 9-10 wins/losses at 50% win chance.
Perhaps now is a bad time to try a martingale. LOL.

Update2: I just won 10 consecutive rolls at 50% win chance.   RNG seems streaky now.  Will take a break and play more later.
My martingale is still holding.  Only 13 consecutive losses will break it.