I've watched 2 episodes so far: one where Bones is accused of bringing a plague to an alien planet & one where Kirk, Spock, and Bones are put in an alien zoo. Both were enjoyable enough but seem lacking from only being 1/2 of the length or a normal TV episode.
I can take the bad animation and not very appealing character designs but the bad voice acting is the worst. It's great they got the original actors but it feels like they are reading from a script not acting. It's actually pretty distracting for me.
I do like that for the most part the animated version has a serious tone. In fact it feels more serious than a lot of the 3rd season.
I do think it is nice to have more stories with the TOS characters but in the end it makes me wish they could have had more seasons of the original show instead (and better scripts overall in the 3rd season of the series).
On another note even if you don't have Netflix all the episodes are also freely available on Cbs.com.