Just did it... Bought the Sharp Aquos 80" LED for my home office...
http://m.sharpusa.com/ForHome/HomeEntertainment/LCDTV/Models/LC80LE632U.aspx
..it's freakin' huge! Have some chilled out IMAX and other 1080p 'scenery' running, as I only have 1 small window in my office, plus PIP a bunch of constantly updating KPIs and key business figures as a constant financial snapshot.
...very indulgent I know, but I make a lot and can afford it easily. These kind of 'treats' are what success is all about.
However, I wouldn't have done this if this 4k 'mattered' financially. It's purely out of spare savings.
And multi-screen setups are imperative for development and anyone on their PC 12-16 hours per day. MakeMeCash is spot on there. Going multi-screen with your desktop monitors (not what I did above, which was pure extravagance) is one of the best financial investments you can make; it really increases speed and productivity.
My main PC is an 8-core AMD with SSD's, 16gb, big gfx card and 4 x 24" monitors - 2 in landscape and 2 in portrait. That desktop area makes work so much easier, as you've got room to spread out. I always run Outlook/Comm's on 1 portrait, Firefox on another portrait, and one landscape is 'assets' and directories/resources while the other landscape is my main work area. This means I have everything at-a-glance. I spend a lot if time personally developing software/tools in PHP and VB.Net.
My first jump to 2 screens converted me instantly; it made life so much easier - not constantly AlLT-TAB'ing between app's. the third made another big difference again, but the 4th was just a little extra space cos I could afford it. I'd always go 4-screen now.
I have 2 SEO servers permanently on separate fast DSL lines which also have 2 screens each and 2 laptops for disaster-management which can do everything the main 2 can do (albeit slower!) - just in case. Plus I keep every OS SSD auto-cloned at the end of every business day, with spare physical drives that are exactly the same for recovery. SSDs can be unreliable sometimes!