I watched the English dub and thought it was mostly solid. The audio quality is much better than the original Japanese voice audio due to the 20 year gap between them being made, but the voice performances are noticeably inconsistent. Some line deliveries are stiff and the actors seemed to struggle with portraying various emotions which was distracting when it happened. However, I stopped noticing these later in the series, I think I was to invested in the show to care about little things like that. It's still a solid dub, but don't expect greatness.
The pacing is my main issue, it takes way too long for things to get going, especially the section on Earth, during which the show feels stagnant and almost aimless. I like the beginning, and towards the end the show really comes into its own. The finale to this show is not just one of the best parts in all of Gundam, but one of the best in any piece of media I've seen. I think the show getting cancelled early actually served to benefit its quality, the pace drastically increased to make sure the story finished in time, making for every episode to be exciting and and interesting with heartbreaking depictions of war on an unprecedented scale. This also means some things got cut down, like the character Challia Bull, who was very important in the novels being given only a small side-role which was disappointing.
The animation is another messy aspect of the show, it often reuses animation and looks awkward, but it can sometimes look pretty good. I think the explosions look great, there was a lot of detail put into them and it adds to the brutality of the show very well even if they're frequently reused. But there are times when I saw weird things, like the Gundam's hand not being drawn, the Gundam randomly having a different weapon in a shot, or the muzzle of the Gundam's beam rifle not moving with the rest of the beam rifle. There are specific instances where the animation looks pretty good, like when Amuro fights the Black Tri-Stars among other cool battles.
The characters are well done, they compliment the situations they're in pretty well usually. This is especially the case when the show gets dark and serious. You get a good feeling of how the war affects some of these characters, which adds to the feeling of how insane the One-Year-War is.
Overall, this is definitely worth watching if you think you can handle an older series with a slow start. This was also reedited into a movie trilogy that has a much faster pace at the cost of some depth in the setting and characters. I personally think the T.V. version is a little better, but the movie trilogy might be a better starting point because of the faster pace. Either way, I highly recommend you watch this series.
