I always get nervous when I see tons of JavaScript. Frankly it's hard enough to deliver a consistent experience in the browser just from a style and layout pers

I always get nervous when I see tons of JavaScript. Frankly it's hard enough to deliver a consistent experience in the browser just from a style and layout perspective. I haven't dug into how it's done, but I feel like JavaScript apps are harder to test and verify. It's not like running unit tests on your server code. To truly verify you need to test the entire application in each supported browser.