I'm using Windows 7 64 bit with Chrome, IE and Firefox for testing.
My problem is, that 14px Arimo Bold looks quite ugly. Letter e looks the worst.
The following screenshot is taken from Firefox but I get similar results with Chrome and IE on Win 7.
I don't know if this distortion is only caused by my Windows PC, so maybe someone could confirm this.
BTW, this screenshot shows processwire with the german language pack.