As for Rebels itself - I'm really freakin' impressed, so much so I JUST finished reading the "A New Dawn" tie in novel.
"Fighter Flight" was the weakest yet, but it kind of felt like a tech demo episode more than anything. I'm not sure if that makes my point clearly, but it felt like something super early that kind of made it too the end, rather than something organic to the overarching story (which does seem to be the case, as 1>2>4 seem to flow very well).
If I have any criticisms, is that so far Lothal seems incredibly boring and we've been back there every week. Now, It makes sense for a home base to be in the middle of nowhere where it IS boring, but visually it feels cheap. The town in the first episode seemed cookie cutter, and everything about Lothal just feels like someone copied and pasted the same rock cone everywhere. I hope theres some more variety coming up when it comes to the visuals, as thats something The Clone Wars nailed perfectly - giving every planet an identity. So far Lothal feels like the neutral planet from Futurama.
As for the characters, I feel we've focused an AWFUL lot on Zeb and Ezra. Kanan got some of the spotlight in the pilot, but Sabine and Hera so far have nothing. Even after reading "A New Dawn", Hera is still a mystery. In a comment over at io9 I said Rebels is reminding me of Firefly an awful lot (which isn't a bad thing) and that Kanan=Mal, Hera=A cross between Inara and Wash, Sabine=Kaylee, Zeb=Jayne and that I guess Ezra fits Simon's fish out of water trope - but now Ezra is feeling more like River in the sense of the "untapped supernatural kid" thing. Anyway, liberally borrowing those character traits has helped endear me to these folks almost instantly. Except Chopper - so far that robot has been a fucking dick. Not mischevious, a dick. I'd have blown that robot out the airlock by now.
The show itself so far has also seemed very "not kiddy" in a way thats surprised me. So far it's felt like we've started halfway through a Clone Wars season (when the show usually picked up and stopped being kiddy). So far we've had the mentioned genocide of Zeb's race with implied flesh melting ray guns, dozens of Stormtroopers killed and zombified remains used as bait. The tie in novel also had a darker tone to it with a much more brutal villain in "Vidian" than I recall in quite some time (beating your enemies to a bloody pulp with your robot hands seems much rougher than Force choking to me).
So all in all I'm hopeful this show can amount to something really good that surpasses Clone Wars (and I really liked Clone Wars half the time). As long as Hera and Sabine get a chance to shine and Chopper stops being a twat, I think we'll get somewhere.