Yeah, the default RAM on the previous mini was 1GB.
I dunno, it's kind of important. The entry-level $600 mini could be used with no upgrades at all and be a very serviceable machine. That was not true previously - the 120GB drive was a touch too small for me, and 160 is more usable. Anything more than that could go on an external HDD anyway. The 2GB is important, because the nVidia graphics use 128MB of the stock 1GB in the previous gen, leaving you with 896MB, which is not enough. While the 2nd GB allows the GPU to use 256MB, the total available RAM is a much more reasonable 1.75GB. For a personal-use PC with typical office/web/email usage, that's sufficient - Snow Leopard is lighter on memory use than Leopard is, and 2GB was good enough for Leopard, even.
edit: the upgrades for the mini are priced way out of line. $599 gets you 2.26GHz, 2GB of memory, and 160GB hard drive. $799 gets you 2.53/4/320.
Upgrading the $599 mini includes:
$150 processor to 2.53
$100 RAM to 4GB
$100 hard drive to 320
$949 - lolwut? If you want the faster CPU, you can get more RAM and hard drive space for $50 by stepping up a model. Why are these prices so insane?
"And and if you start to bleed, stop wiping." -whm1974