Now that Adjustmen Brush is totally awesome and extremely useful, here's some feedback that would make it even better.
1) Save brush settings A B C or something to reduce time requred to shift the settings when applying multiple adjustments over and over.
2) Reduce the need for 1) but making the adjustments smart. Apply adjustment to one image and then copy/paste it to the second image. LR analyzes the input area and corrects for offsets/scale/rotation in the destination image. The user can then make further movement corrections by dragging, rotating and enlarging via the pin.
3) HSL for the brushes would be huge. A wedding dress often takes on a blue hue. It would be 10x faster to desat blue and swipe over the image and not affect the green grass and skin tones around the dress.
4) Mask for ND. In the case of open sky with subjects heads protruding up, have an adjustment brush that can mask out the ND.
5) Allow photoshop-like Click-HoldShift-Click to make adjustment lines from A->B. There are many straight lines in architecture and nature. It's tough to trace but the clickA-shift-clickB is a wonderful tool in Photoshop. Bring it to LR.