Yeah, I’m not convinced Helvetica is great for articles, so I’m still reflecting on that myself. I do see lots of fonts I really like online, but usually they are pretty fancy, served up by services like Typekit.
I’m also not convinced that serif fonts are so bad for text. Sites like a List Apart are quite happy to use Georgia, and I find that a better reading experience in many ways.
It will have some effect, but Google is pretty well optimized. I’m sure there are stats out there, but it’s also easy to test. Sites like WebpageTest will quickly show you the difference if you run some tests with and without web fonts.
You could also just serve the web fonts to desktops, too, if you choose.
Yes, me too, although it’s a little quicker with that extension; and when you are doing it a lot, it makes the extension worth having. (I only use 4 extensions currently, as they are the only ones I use pretty much daily.)