I love TAS. It was actually the thing that I watched the most of Classic Trek wise when it aired in the UK in the mid 90s. Other than that I was always just the films and TNG onwards.
Same here! In fact, those mid 90s repeats could have been one of my earliest introductions to the world of TOS, long before I ever got to see the live action series or the movies.
As for the frequent complaints -- sure, the animation was occasionally dodgy, but I'd argue no less so than most TV cartoons of the seventies. There was a lot
of cutting corners in those days right across the board.
But in my estimation, TAS is just made of win. How could it not be? It's essentially 22 extra episodes of TOS complete with the original actors. I love the way Filmation put real attention to detail in, too. Oh sure, there are pink Tribbles and other occasional errors, but I love how for example the Enterprise fly-bys were done by actually taking stock footage from TOS and rotoscoping. Or that the interior sets of the Enterprise are basically identical to the ones seen in TOS. Little details mean a lot, and TAS really does strive to be faithful to its parent live action series for the most part. That it has been so neglected within the fandom for so long is regrettable.