I noticed yesterday evening that one of my systems running Linux Mint 201109 Gnome was offering to install Update Pack 3. This morning I see the release announcement for it. This is going to be particularly good news for some users with very new hardware, because it upgrades to Linux kernel 3.0. On my HP dm1-3105ez, for example, this means that it now includes the driver for the Ralink 5390 WiFi adapter. Of course, there are a lot more changes and improvements in this update. If you have been running the normal distribution with Update Pack 2 installed, it will probably install something like 480 updates.
There is one thing you have to be careful about, which is explained both in the Update Pack description that you can get on your Linux Mint system by clicking the button in Mint Update, and in the Update Pack release announcement mentioned above. The Debian security and multimedia repositories are now included in the Linux Mint hierarchy, so you need to change the software sources list on your system accordingly. It is not a big deal to change, it takes about a minute, and there are very good instructions in the Update Pack release announcement.
Until now I have had my HP dm1 netbook pointing at the Linux Mint "Incoming" repos, so that it already got the Ralink driver. Now that this Update Pack has been released, I changed it to point at the "Mint Latest" repos, and then refreshed the update list. It only needed to install about four or five updates, and everything was done. Very nice.
This is essentially the first iteration of how this "Update Pack" system is going to work on Linux Mint, and I think it looks very good.