Product review (5 stars): Nice Unit - Sort of tight fit
Bought this from Amazon via Build.com.  It was drop shipped direct from Zephyr.  Took a little over a week to get.  Installed myself (see below). Replaced a bottom of the line Broan power pack.

Performance wise we are happy with it. Quiet on low speed, typically somewhat loud on high speed.

Quality wise it looks like a good product.  Fan is a squirrel cage with apparently 3 bearings, which is good.

Comments and Suggestions:
- This is much bigger than the Broan power pack it replaced.  It ended up being a tight fit on width.  This was attached to a plywood mounting board that then slipped up inside the kitchen vent stack and screwed on to frame/mounting boards.  The unanticipated problem is that the unit is attached to the mounting board using horizontal (not vertical) screws on the width sides.  This ment I had to put 1x2 strips on the inside of the mounting board for the horizontal mounting screws to attach to, this was easy enough to do.  The problem is that it increased the effective width by 3" (1-1/2 screws sticking out on each side).  I ended up taking out the screws and cutting them to the exact length needed to get through the 1x2.  Anyway, it took me 4 trial fits to get the unit plus mounting board to slide into the space available.  Alternatively, you could lift the fan unit into a previously installed mounting board, the unit has a clip to make this easier.  However this makes it somewhat harder to attach the vent connection due to less access space.
- The unit is well packed and has 2 large styrofoam packing enclosures.  I recommend keeping these for the installation.  They were the right size and very useful for stacking / elevating the unit up into the vent stack.
- The unit is heavy enough that it helps (saves time) to have 2 people to lift it into final position.
- The outer face of the unit comes tightly screwed to the body.  If you want the face to fit tight to the mounting board, you need to loosen these screws by a 1/4 inch or so before attaching the body of the unit to the board - then tighten the screws.  Otherwise you will have a slight gap at the edge.  This is not suggested in the instructions, which are less DIY focused than Broan instructions.