At Monkee-Boy, we use the constantly growing Google Fonts collection for our web font needs. This comes with several performance benefits: popular fonts are more likely to be cached, Google’s servers are extremely fast, no need to convert for the web, and great selection of fonts.
The right font plays a vital role in great design, but it’s important to note that if your site takes too long to load, the visitor is more likely to leave before even getting to your content. Luckily for us Google knows this and provides an awesome tool that shows you how different fonts will impact your page load.
I recently wrote a post for the Monkee-Boy Blog about quickly testing your Google Fonts. Basically it all comes down to keeping an eye on the number of fonts and font-weights you are using. Performance testing might be something you do at the end of a project during a QA phase but it's an important part of every project and deserves more attention early on. I'm lucky enough to work with a talented design team who understands and cares about performance just as much as the development team does. The post doesn't get into any technical performance details and instead is a high level overview so clients understand why selecting 4 fonts and 25 font-weights is not a good idea for their site.