First the design. Immediately noticeable is the huge chrome plated logo. So far all AA1s were rather shy about their name. A bit less prominent is the faint pixely grid on the matte cover.
To the internals. The AO521 is powered by an AMD V105 processor. This is the slowest single core "Geneva" processor of the "Nile" platform, clocked at 1.2GHz, with 512KB L2 cache, DDR3 support and 9W TDP. Performance and further details remain unknown until AMD announces it in May. It is paired with an AMD M880G chipset with integrated ATI Mobility Radeon HD 4225 graphics core and 384MB dedicated video memory. The 4225 is not announced yet either and probably has a few minor architectural improvements over the 4200, hence the increased model number, but is likely slower due to 25% lower clock speed. It supports UVD2 and Acer didn't forget to add an HDMI port.
The battery is rated at 7 hours. No other interesting new features except for optional Bluetooth 3.0+HS support. Included in the package will be a new compact and light power adapter, with interchangeable plugs, called MiniGo. I have no specific details on price and availability.