Hello,
First I would like to say that since USB 3.0 is not officially supported by Apple, any USB 3.0 adapters you may buy will rely on a driver from the manufacturer. In LaCie's case, this means the adapter will ONLY work with LaCie external hard drives. And since nothing beyond storage devices are supported by the various USB 3.0 drivers for Mac, it makes the interface only a complicated but theoretically faster eSATA. So, if you're looking for an external storage solution, I highly recommend an eSATA adapter. Steer away from USB 3.0 on the Mac.
Second is that I use the ExpressCard slot on my MacBook Pro for video capture. A product by MOTU called the HD Express (
http://www.motu.com/video-products/hd-express-hdmi) allows me to capture content from HDMI, component video or composite video / S-Video sources, making it a handy little box to capture just about anything. This product works only with Final Cut Pro 7 however, and is clearly geared towards the professional Mac user (I personally use it for less advanced setups, like capturing the output of my gaming console). For $500 USD it's certainly a cheap option compared to other HDMI capture cards, and all this through the ExpressCard is certainly amazing.
Other uses for ExpressCard: if you're a video professional, some Sony XDCAM camcorders use SxS storage cards, which can be read directly with an ExpressCard slot. Photo enthusiasts will be delighted to have a CompactFlash to ExpressCard adapter at their disposal, music producers will be just home with professional audio products like ECHO Indigo IOx (a professional sound card with a single input and output). SSD cards in ExpressCard form are also available from manufacturers like Transcend.
There are many uses for ExpressCard, however beyond typical use (such as a card reader or 3G modem), you will find that most products are in the professional range and as such demand a premium price, too. For the professionals themselves these products will come very handy, and most are reasonably priced (like the MOTU HD Express I own).
~Yousif