Hi, thanks for your question and for thinking of Plugable. You should not have problems now with OS X 10.6.8 or if/when you upgrade to 10.7.2.
There were a lot of concerns about how graphics adapters using DisplayLink chipsets performed on OS X 10.7 last summer, but these have been addressed with a new driver from DisplayLink available here: http://displaylink.com/support/mac_do…. Make sure to review the limitations with 3D acceleration that DisplayLink mentions.
As far as which adapter to choose, it all depends on the type of external monitor you want to set up.
What resolution do you want to use on the additional monitor you would like to add to your computer?
Does the additional monitor have VGA ports, DVI ports, or both?
What applications are you likely to display on the external monitor?
Your answers will help guide the recommendation I make about which adapter to choose. If you have additional questions about our products (http://plugable.com/products)), send them along. We’re here to help.