So I bought the shroud kit since the bay in the W30 gets pretty hot after driving, even after just a little bit, and it looked like a nice piece of engine bay bling (with the added bonus of being pretty effective). I can without a doubt say it is very effective.
It mounts using the four bolt hole locations that the rain guard uses and can be used with the insulation on the OEM engine lid as well as the original rain guard hardware. You also have the option of using the supplied hardware. I got the option with the plug and play harness because I'm lazy, but I'm sure wiring it up yourself is not difficult and would take a days work if you're good about it.
With that said, the harness is very neat and has just enough slack so that it's not pulling on the lid but also does not sag and rest on anything; it also comes with a wire that activates the fan relays so that you can operate them however you wish.
Be warned, the whole assembly sits about 1.5-2.25 inches below the lid skeleton and will not clear a rear strut brace with a crossbar. It may be possible with a custom one that bends down in the center but that is just a guess. It clears the stock one just fine.
For reference, I have the MWR alternator pulley and an underdrive crank pulley for the 1zz on my car currently, as well as a 2zz water pump. I would not advise running it constantly like I did (for a 2.5 hour spirited drive) because it might drain your battery to the point of a "no-start" as it did mine. This of course was with my setup and your mileage may vary but I thought it'd mention it anyway.
Note that, as with all aftermarket parts, there might be some issues. For mine, there were just 3 things:
1) If I bolted 3 of the shroud holes, one would not line up. I reamed 2 of the holes just enough so that I could bolt all 4 locations down.
2) The latch cutout on the shroud itself was placed far enough down that it collided with the latch assembly on the car and also scraped the lid hook. What I did was cut about a 1/4 inch off at the top of the shroud (to clear the latch assembly) and ground about 2.5mm off the top of the section of portion of the cutout meant for the hook (so that it no longer scraped it).
3)There are bracings on the top and bottom of the shroud that are welded meant to support the main bend. It is meant to look as neat as possible so the wiring is routed between the shroud and lid; on mine, the rear shroud brace would pinch the harness so I had to cut a large slot so as to not cut the wiring. I was told later orders would come with a cutout.
I was prepared for any issues I might encounter and had no problem making necessary modifications.
Overall, I am very happy with the shroud kit and would recommend anyone who wants to vent the heat to seriously consider purchasing one.