I agree; it is a great little machine! IMO it does need a bit more ram for most users. The standard Mini, whether 2010 or 2011, really doesn't have enough ram and the slow hdd hurts it even more. My Mini gets a fair amount of use from as many as four users logged in at once and all running typical apps such as Safari, Mail, iPhoto and others, not to mention a bit of gaming thrown into the mix. Even with all that going on activity monitor reports I am usually using somewhere between 5-7 GB so I still have a little cushion but 4 GB would not be enough for me. A matched pair of ram should run slightly better than 1+4 or 2+4 but you probably would never notice the difference in real world usage. Only a geek setting up a Mini server farm would worry about that, LOL.
I bought my ram from OWC but, as a previous post said, you can order from those other vendors as well. You would be buying at a great time as well since 2010 ram is less than half the price when I purchased mine.