This new feature has been in the works for a while now and you will now see a big difference in future updates released.
For a full description, please read the Lavasoft Research Blog entry here:
Lavasoft Research Blog
New definition database reduces defintion file size
http://www.lavasoft.com/support/securitycenter/blog/?p=318
That is especially good news for our dialup users, and should also make updates easier for everyone
