I saw the little text box at the bottom jiggle at me and immediately closed the page.

#1 PROTIP to a good UI. Don't jiggle anything, anywhere, ever, for any reason.

Some points are about UX, others are about marketing and conversion... "Good" is from the POV of the business, what is best for the business isn't always what's best for the user. I, for one hate the large call to action/subscribes that pop up at the bottom 1/3-1/5 of the screen, such as on this site.