For the most part, I think that standards have been good, in particularthe way that certain referee / TMO combinations have liaised in order to scrutinise incidents without delaying the game has been great.
My only frustration is one that I'm surprised that more hasn't been made of - the occasions when TMOs have spotted incidents, which they and the referee have reviewed and decided on the wrong (according to a citing hearing) sanction. It demonstrates conclusively that one or the other are making the wrong decision. An an arm chair fan, it's impossible to pinpoint who gets it wrong and why, but it's unfortunate that someone is making the wrong call, especially now we are reaching the business end of the tournament.
I have more sympathy for incidents that both the team of three and the TMO have missed - the TMO is just one person with one pair of eyes and god knows how many feeds (no scrum related pun intended) to keep an eye on. It's unfortunate, but understandable.