When I bought the Acer Aspire One 522 some months ago, I was thinking of upgrading the memory almost immediately, because it came with only 1GB installed. Two things stopped me, one small and one large. The small one was that Acer only offered the system with 1GB of memory, and while they didn't explicitly say so anywhere, I got the impression that either the system itself or the pitiful Windows 7 Stupor Edition it came with wouldn't handle more than that. The large one was that I couldn't figure out how to open the case, anyway.
I happened to think about this again this week, and I figured that enough time had passed that there would probably be some information on the internet explaining how to open the case and upgrade various bits. Sure enough, there are plenty of descriptions out there now, and even a few videos on youtube. It turns out that the reason it is so difficult to get into is that the screws which hold the bottom panel on are actually underneath of the keyboard! So what you really have to do is figure out how to remove the keyboard, then the rest is easy. Even that is not so difficult once you know how - there are four small retaining tabs sticking out of the case holding the top of the keyboard in place, they are located just above the F4, F8, F12 and Del keys. Press those gently out of the way with something BLUNT (not a knife!), and you should be able to lift the top of the keyboard gently out. If you can't get it to come up, you can remove the battery and then use something BLUNT to press gently upward through a small hole you will se near the battery connection.
There is a ribbon cable connecting the keyboard to the case, you can either leave it connected and work carefully around it, or slide the connector forward and release the cable - warning, reconnecting that ribbon cable turned out to be by far the most difficult and tedious part of the entire procedure. Remove the eight screws you find under the keyboard, and then you can pop the bottom cover off. The memory card, disk drive and various other bits are right under that cover.
I got a 2GB DDR3-1333 SODIMM memory card for 30 francs, and it works like a charm. I checked the BIOS the first time I booted, and it reported 2GB memory, no problem. I booted Windows 7 Stupor, and it reported 2GB as well. The same is true of all the various Linux distributions I have loaded on that system, as well. The AO522 boots faster and generally performs better. There is no huge difference in speed once it is actually doing something, but there is a lot less hesitation when starting a new task. This has worked so well, shown so much improvement, and the memory was so cheap that I will probably do the same to a couple of other systems too.