Hi,
I am a Mac user, and I have a USB Display-Link adaptor from Buffulo. I bought it from Japan and it support display up to 1600x1200. Currently I am using it with my MacBook Pro and PowerMac G5. So far no issues and I am using the latest OSX driver downloaded directly from Display Link website. Basically using the driver utility, you can either mirror the 2 displays or extend it. Very useful in photoshop and lightroom.
Display-Link itself does not sell the gadget, it is a technology company. But there are many vendors in the market today that OEM Display-Link technology. IO-DATA, Buffulo, etc..
So far I have no see any branded USB Display-Link adaptor been sold in Singapore. You might find some "china-made" ones but i'm not sure about the quality and the resolution it supports.
Depending on the model and type of USB Display Link adaptor, the driver utility can support up to 6 displays. The most common type is the Single USB Display Link Adaptor, basically one end is USB the other end is a DVI.
Example, if your MAC PRO has 3 spare USB port. You can buy 3 USB Single head Display Link adaptors and plug them into the Mac PRO. INstall the driver and now you will have a super extended display. The original display (connected via DVI to yr orig display) + 3 additional displays (connected via USB).
One of the usage I did was:
Orignal MacBook Pro display is my primary OSX environment, then using USB Display Link to an exterior monitor I start vmware fusion and run Windows on that display. Dual display with dual OS