Although upcoming release may solve font usage issues (to include Google fonts), I found that @font-face with SVG fonts works with current (1.3.1) TideSDK release. For example, download TangerineBold "Font Kit" from Font Squirrel -- only need the SVG font. Then include the following in your style sheet:
@font-face {
font-family: 'TangerineBold';
src: url('Tangerine_Bold-webfont.svg#TangerineBold') format('svg');
font-weight: normal;
font-style: normal;
}
and style elements with:
font-family: 'TangerineBold';
Further explanation (added 3/19/2013): I have given more details of custome font usage in TideSDK 1.3.1-beta on my blog, here