Conroy's voice is still great but he is getting to old to play a younger Bruce as seen in the Arkham games. I feel very similar in regards to Hamill's Joker.
I think people are stating that the animation hasn't really held up compared to modern animated series. As a fan of animation I can totally understand the critique as it lacks some of the fluidity that modern viewers expect. However I believe that is part of the show's charm and even is used as part of the narrative artifice as the show recalls film noir which was a genre/mode of B-film production.
Some people are voicing narrative concerns but this seems to be a reflection of age as the show was intended for a younger audience. My nephew and niece both love the show whenever I put it on for them, even in the few moments where I roll my eyes. I haven't shown them some of the darker episodes that constantly appear on people's lists of best episodes, I can't wait until they are ready to watch Robin's Reckoning as it is my personal favorite. They respond equally well to Batman Brave and the Bold which makes me think that they have great taste in cartoons.