For me, I love TAS, but I'm coming to it from not just a Star Trek fan perspective, but as an amateur animation historian. From an animation perspective, the Filmation years were really interesting and I would go so far as to say important to animation. Filmation and Hanna-Barbera, while both used limited forms of animation, basically invented Saturday Morning cartoons and really made tv animation acceptable to the masses. Far better animated properties from the 80's, 90's and today would not have existed with Filmation and H-B.
Now from the Star Trek perspective, until the DVD's came out, I had never seen an episode. It was 2009, I was really missing Star Trek on tv and that dumb JJ-Trek film was fresh on my mind. I was really missing the Star Trek I became a fan of and feeling really down that outside of JJ-Trek, it was all done. Then on a random shopping trip, I ran into TAS for $15 (sale price mind you) and decided to give it a go. It was like finding lost Star Trek I didn't really know existed! It actually got me excited about Star Trek again.
I really see the two seasons as the last two years of Kirk's five-year mission, and unlike fan films (no offense to the hard working fans that make them), it was actually made by a lot of the same people that made TOS! For me, the main things I'd love to see changed however on a possible Blu-ray would be fixes to various glitches in the show (i.e. the voice of one character coming out of another character's mouth, etc.) and the much need color correction. Poor Hal Sutherland as I understand it was color blind, but it would be nice to see Klingons, Kzinti and Tribbles in the colors they were meant to be seen in.