Not their best. Takes some getting used to if you're used to their "older" (read: previous) stuff. But, with that said, it's not bad, and I cannot warrant giving it a thumbs down. Any Orbital fan won't doubt they have talent--ultimately, it would be difficult for them to produce a bad album if they tried. And yet I give this a "so-so" rating, namely because, if one has never heard Orbital before, this is not the album I recommend that they start with. It does have a bit of an "acquired taste" you could say in that you don't just pop it in and--voila!--it immediately grabs you just like that. I think with Orbital fans, it might be hit or miss. As I said, it made me slightly disappointed in that I longed for the OLDER sound. But it was not something I did not enjoy or would not listen to on occasion.
As for what exactly doesn't make it as "good" as the rest, I admit that it has been a while, and (sigh), it's always hard to put into words what makes "good music" and what doesn't. To me, good music is no more than a sequence of notes and sounds laid down in a certain sequence which ends up--either purposefully or by accident--producing pleasantry among my brain waves (or pleasant feelings when my neurons fire off)... That's why it's almost impossible sometimes--with a vague genre like techno/electronica--to say in words "why" one album surpasses another. Perhaps it may just be worth a listen, and then you can be the judge.