Before loading this save file, make sure you are set to Peaceful. This is for the purpose of pistons not getting stuck once you load the world due to mob spawn conflictions.

Also, you may lag, so have your settings to minimum, as well as smooth lighting turned off.

This trap has been tested dozens of times on a clear map, and produces anywhere from 128k to 133k items per hour. Most testing ended around the 130k range.

You can also edit this in MCEdit and make the spawning floors 3 high for Endermen. Testing that build, it will give you around 2000 pearls an hour.

0 silk is produced, but you can also remove pressure plates and pistons from certain cells and add wall signs after widening the fall space to 2 blocks, so spiders will spawn. I would suggest splitting the map in half, then splitting those as well, to see how each quarter build was done.

The only downsides are over time, pistons will slowly get stuck. Slimes may spawn in the bottom parts, but it is rare, and they will despawn. After 15-20 uses on Easy, Medium or Hard to get a full inventory, you may want to reset the trap using MCEdit. If not, the stuck pistons will start to effect the drop rates.

I'm currently working on a system that doesn't take any of the current spawn space, but will be able to reset all of the pistons in the trap with the push of a few buttons at the collection area. While tricky, I have high hopes it will be possible.

Additional Notes

Also, for people asking how to test a trap, I would suggest this method:

Have a timer or stopwatch. Change your difficulty from Peaceful to Easy. Once you actually hit the escape button to unfreeze the game, is when your time starts, because that is when spawning starts. 60 seconds in, hit escape again to bring up the option to go back to Peaceful, which will also at the same time freeze the game and prevent more spawning. It's very accurate if you do 1-5 minute tests.