Ok, my 2c is that BTC is the future of online poker. i have been playing professionally for over 5 years (not anymore though). Best BTC poker sites I have played in the past are, a) Nitrogen (cash games, not all the time lots of actions, but can be fun and profitable), b) Betcoin.ag (not much cash game action, a lot of tournaments with big payouts), c) sportsbetting (they accept a few crypto's, easy deposit, but they might ask for personal info on withdrawals. I had never encountered a problem withdrawing my funds).
5dimes/Grand Poker also has/had good action from times to times.
Obviously, not many poker enthusiasts own or want to buy BTC to play. So the best choice for action is websites that accept BTC, but work with a well-know platforms, that have players from a few different websites, that also accept fiat.
There are a reasonable % of players who do know or own bitcoin but the players go where the games are and the games are mostly at pokerstars for the last 8 years. When they have bitcoin games everything will be great!
Obviously Pokerstars is winning but since Black Friday, a lot of sites are catching up. Also, enthusiasts that have bitcoin as an investment don't want to risk them on gambling.