To me, it's a major step down from DP in terms of writing and character development, and it's gone even further downhill after the Team Plasma episodes were (seemingly pernamentaly) dropped. Ash has been flanderized down to his season 1 self, and most of his Pokemon have barely any to no personality at all, just soulless battling machines, I see his BW team to be the complete opposite of his DP team, in which his DP Pokemon such as Infernape and Buizel all had their own distinct personalities, in BW, the Pokemon are just "Send them out to battle and only to battle", with only, at most, two of his Pokemon (Snivy and Oshawott) actually having personalities at all (not to mention that those two are shown more than an of his other teammates outside of Pikachu), though those two (and to an extent, Emolga and Axew) tend to often annoy fans, they are pretty much the only Pokemon that have personalities at all, with more focus to the human characters than the tituluar superpowered animals.
In terms of the human characters, Iris and Cilan are pretty much among the few good things about BW (which I will discuss later). Bianca is the complete opposite of her game self, in the games, she was a determined trainer who was willing to do the right thing, though tended to be a ditz from time to time, in the anime, she's a hyperactive ditz who has no idea what she is doing at all (basically, a female version of Barry, but with her IQ significantly dropped by several points lower than Barry), despite that, her most recent appearance has shown that they are starting to make her act a bit more like her game self. Trip is basically Paul, but with everything that made Paul an interesting character completely stripped, with nothing left but a total jerk, whileas Paul recieved character development over the course of the series. I find Burgundy to be incredibly annoying (although that may just be me), while Langley (I refuse to call her "Georgia") has more potential than most of the other rivals.
*sigh*, if only N was in the anime...
Among other bad things include the Gym battles, which are incredibly generic and boring (Castelia and Nimbassa Gyms being the worst offenders), as well as the random fillers after Castelia City and don't get me started on Team Plasma or the black Team Rocket uniforms, enough blood has been shed over that topic already.
Among the good things BW has given us is that it's very colorful, the music is wonderful, and the animation is very fluid, not to mention how interesting a few of the characters introduced in the series are (namely Iris and Cilan), and Iris has a truly interesting backstory, the chemistry between the main trio is also very well balanced.
The only truly bad thing is Ash's regression.
Back in DP we had watched Ash finally become the experienced and great trainer he was supposed to be, while still retaining his personality and being still Ash...but now its all been reset.
Its sad to be honest. The DP version of Ash represented all his growth over the 13 years of the show....and now BW Ash feels like that's all been washed away.
Agreed, the BW Ash is an absolute joke compared to the DP Ash, it's as if BW is an alternate continuity where Ash never went to the Orange Islands, but if that was the case, then wouldn't Misty and Brock still be travelling with Ash, it's just so confusing.