For a long time, I was looking for a MMCplus card that does better than the usual 10-12MB/s. The A-Data Turbo 200x MMCplus 4GB shows about 31MB/s read and about 11.5MB/s write. The read rate of 31MB/s might already be limited by the USB 2.0 transfer rate, but is still 30% faster than the current SD standard would allow in theory. As the results with the Hama 35 in 1 V3 show, there are still card readers that only use the 4-bit interface of MMCplus, either due to the card socket, board layout or controller. There are even card readers using an 8-bit socket, but a controller with 4-bit MMCplus support. Please note that the 4-bit mode of MMCplus is still as fast as the current SD standard, as the 19.1MB/s compared to USB 2.0 SD readers show.
Currently, the MMCplus standard is the third fastest memory card standard with a theoretical limit of 49MB/s. CompactFlash 4.0 offers a theoretical data rate of 127MB/s and the Memory Stick PRO-HG offers a theoretical data rate of 57MB/s. While CompactFlash can be accessed in ATA mode, and SONY offers the MSAC-EX1 ExpressCard PCIe x1 adapter, there seems to be no way to make use of the full speed of the MMCplus standard. The good part of this bad news is that there seem to be no devices that can take advantage of the MMCplus speed, making this memory card standard more or less obsolete.
The CompactFlash standard builds on the popular ATA standard, that was already fully "grown" due to the increasing harddisk speed. Memory Stick PRO-HG is a completely manufacturer driven standard. If somebody at SONY decides to introduce a new standard, somebody at SONY will build a card for the new standard, and somebody at SONY will build a new card reader that can deal with the new standard. And finally, somebody at SONY builds a new camera that can make use of the new stadard. SD and MMCplus are both only driven by the respective association, and both build on the original and very basic MMC standard.