Used in the header, they will not assist in SEO (nobody searches for 'Penn & Teller')
Also most SE's will not render them correctly, so they look silly. 'Penn & Teller' might stand out among a serps page full of "Penn and Teller"s, but not for what one might call 'good marketing reasons'
Finally, it's very 2003; it was briefly a fad until Google got bored and stopped showing them correctly - now, 90%+ of the time, they don't work.
Used on the page they will show correctly in all modern browsers (if the page is built correctly), but the Hx tags are important, and should reflect possible searches, not impossibly unlikely ones.