I installed Office 2013 through the bundled Office 365 Personal subscription, again, a $69.99 value, and after a few other app installs it's at about 10.3 GB free. Absolutely fine for casual use.
I've tested MS Office 2003, 2007, 2010 all work as you would expect. Also, tested LibreOffice; a little slow on startup but fine afterwords. MS Office 2013 slows on excel macros or large excel files and slows while importing video into PPT. I wouldn't dare us MS Access on this machine.
HP Stream 11 はﾃﾞﾌｫﾙﾄのﾒﾓﾘが 2GB なので､MS Office に限らず Windows8 を動かすには､やや非力な感じが否めません｡
せめて 4GB あればという感じがします｡