If you're not familiar with the game, here's the wiki article for you.
I love the game's plot, and it's no different here. A few changes are made, but overall, it's great.
While the scenery is lovely and well-drawn, the characters look nothing like themselves. I honestly think, if given enough time, that I could do much better than the animators did, and I have very little in the way of artistic tale.
Celine Jules, one of my favorite characters, was turned into a Sailor Moon clone. This, IMO, is unforgivable, as Sailor Moon is an affront to my very existence.
They also butchered Rena's design, turning her from this:
Nightmare fuel, IKR?
Awkwardly-placed plot exposition ahoy, and that's not even mentioning all the random (read: stupid) crap that was thrown in in an attempt to be funny.
Plz to be sticking to the original game, kthx?
Not gonna lie, I didn't like the voice actors at first. I really enjoy the VAs in Second Evolution, so I was seriously weirded out by the new voices.
However, they did grow on me a bit. They do have a few problems (Rena's voice actor in particular, oh Gaia no), but overall they did an okay job.
I love the original characters, and EX is fairly faithful to the source material. Rena is still the sweet, naive teenager she was in the game, and Claude is still the slightly clueless but enthusiastic guy who goes around with no idea what he's doing.
However, Ashton (my second favorite character, nooooes) has been turned into simple comic relief, something that just Should Not Be.
Admittedly, he is the physical embodiment of the Crouching Moron, Hidden Badass trope, but that badass bit is tacked on for a reason.
Overall, the characters are decen, but they could have done better.
Entertainment value: 8/10
When it's good, it's super good, but when it's bad (like it is most of the time) . . .
. . . well, you just can't help but laugh (in a snarky matter, of course) at all the problems this thing has.
All in all, I wouldn't recommend this to any non-Star Ocean fans. It's only worth watching for the lulz and for fic ideas.