For popular fonts this will likely be slower and use more network access.
If they have already visited a site that uses the font you use by putting ?text= on the end you're forcing the browser to go off to Google to get your subset even though the full font file is sitting their in their browsers disk cache.
Lovely. I want to add that you can do the same thing with fonts you have bought somewhere else with a free tool like fontforge. I recommend this to everyone who has a high-traffic landing page. It’s pure money!
David Ojeda, This is a great tip. Thanks for the write-up.
Shannon Crabill
Full Stack Software Engineer
I was just picking out custom fonts for a project. I'll try this update next time I'm working on it.