There are some (a very few so far) of the components and updates Microsoft which will require the new installer, but we do not have a list. There are none that we use. They include some of the latest releases of Windows Live, Office 2007 section Service packs Sliverlight 3, and some of their system tools... But microsoft will automatically update you to the latest installer if needed for installs. it is clear that Microsoft intends to have the new Installer be controlling for all new issues.
No other products we know will require the new installer....
There are no issues reported that would make one avoid the new installer... other than the standard stuff