Gold/iron pressure plates only activate with a stack of items on them- yet there's not a way to retrieve said items after.
Trapped chests emit a redstone signal, but have a different texture to tell them apart (so you know the chest is trapped- just swap the items out with cobble)
The comparator (a piece of redstone logic) is somehow a magical inventory detector- rendering said trapped chests obsolete*. Its signal varies with the amount of items in the inventory, except a jukebox when it emits a different signal with different single items.
*except as an odd way of stacking chests next to each other.
(All that functionality could be achieved by making the iron/gold plates as part of the trapped chest for signal, and keeping the comparator as a logic piece only)
Nether quartz was added to encourage gameplay in the nether, but as a easy to find mineral of little practical use (apart from '
pretty blocks'), its nothing more than a smash and grab to consider with collecting glowstone or tracking down a fort.
Hopper can auto-collect items and dump into an inventory (good), but can also magically suck out of an inventory, and (
despite being a gravity-fed mechanism), can connect sideways to form long pipes.
Remember dinnerbone was originally hired to build a functional mod API- due to be released in 1.2-1.3, we're now seeing "features" for 1.6 and still no sign of said API beyond rumours and speculative deadline of what may/not happen.