"Transparent Mining" allow each user's client to automatically determine who will generate the next block, so that they can then send their transactions to that node. This will also allow additional fees to be realized for immediate/priority transactions.
An equally important feature of Transparent Mining is an outstanding security feature of the protocol to temporarily reduce to zero the mining power of nodes who should generate the next block but don't. This transparent mining feature will prevent against even a 90% majority owner of all NXT branching out and forcing a fork. So if a node that has 90% of all NXT, and doesn't generate a block when scheduled, the system will reduce its mining power to zero temporarily to prevent a bad fork from being forced.
This feature is planned to be implemented partially with block 25000.