As a long-time reader of all things Dredd, I can honestly say I couldn't care less about the actor not being some kind of beefy bodybuilder. IMHO the character suits being lean, lanky and mean, as the fundamental idea of Dredd is that he's a 100% physical incarnation of the Law itself - so he doesn't a very impressive physique to do the talking for him: His blind devotion and sheer mentality in itself is enough.
Clint Eastwood 15+/- years ago would've made for a sensible choice of actor in my mind. Old, grim and stringy enough to play the part, and with that Dirty Harry frown to go with it. Looks like Urban tries too hard to pull this off, I'd rather see them go with a more characteristic-looking actor. Doesn't really matter if he's famous or not. Stallone sucked as the judge anyway, and the whole movie turned out to be a steaming pile.
In regard to the costume: Don't care much for all the straps and extra padding on the chest, and I think they should've kept something more like Stallone's shoulderpads for this version too: huge, oversized, intimidating gear.
That being said, the helmet could've been somewhat smaller, and I don't care much for the fact that they kept the entire visor black, not keeping the bottom of it clear like in the comics - I don't see why they changed that.. Glad they kept the upside-down "V" though.