Honestly, I expected 16:10 monitors to have disappeared by now. Thankfully, they still exist at the mid to high-end, especially amongst IPS displays (NEC, HP ZR24w, Dell U2410). I was considerably more surprised to see 2560x1600 revived with the Dell U3011 and HP ZR40W. After Apple abandoned 30-inch displays for the 16:9 27-inch, I figured 2560x1600 wasn't long for this world. 16:10 persists amongst more costly notebooks as well (eg the MacBook Pro, which is universally 16:10 from 1280x800 to 1920x1200).
To my mind, the more pixels, the better. Vertical is a more pressing concern in larger screens because human beings like to read vertically (take a look at your books, magazines, web pages... how many are wider than they are tall?), but most panels are wide. It's easier for eyes to scan down than to sweep left to right over a large expanse. That's one of the reasons why the iPad and other slate/tablets make for easier web-browsing and text-reading than similar resolution but horizontally oriented netbooks.