Yes I've seen up to EP9 and so far I've liked it, certainly more than I did BOBF and more than half the shows currently running right now. Sure there are a few parts that I didn't really care as much for compared to others but that can be said of any show. As for lore I'm not an expert and honestly I'm fine with Master Chief taking off his helmet in this context because he's a character we're following thus we don't need to feel the character can be anybody like how the game was intended to be to make the player feel like they're the hero. I'm not aware of all the other criticisms other than the helmet removing issue so I can't speak to them, then again my being a more passive fan of Halo maybe I'm able to enjoy it more than a hard core fan.
Obviously due to streaming budgets the CG isn't to the standard of a feature film but I give them credit for doing their best on the Covenant species from the Elites to Brutes and even the Prophets, they look pretty good considering. The show does seems very story focused with only a limited number of action scenes, again likely due to budget and the CG eating up a lot of that. In terms of casting they characters seem to work well but since I'm not too familiar with all of them so I wouldn't know if the casting is spot on.
The one aspect that was off for me was Master Chief's height compared to other characters, in the games he seemed very tall while in the series he just appears to be taller than an average person. I think it's definitely worth checking out and if you're a hard core Halo fan perhaps going in with an open mind. I mean I certainly understand those feelings as a hard core Star Trek fan and seeing the crap the current team in charge is putting out, and with each new show I try to go in hoping it's better than the last only to be disappointed. After all when you area fan of a franchise spanned decades with set rules and the new generation decides to throw it all out it can be frustrating.