You can never have too many monitors. Time is money. If your going rate is $50/hr then that means the company you work for pays $100/hr for your time and clients pay $200/hr for your time. At that rate, all a monitor has to do is save 1-2 hours of your time in order to be worth the price (depending on the monitor and keeping in mind electrical costs as well as the computing power necessary to drive that many displays).
I used to have 4 monitors for my desktop plus 7 mobile devices nearby. These days I have a giant 4K TV as my main display (which replaces 4 monitors) plus 4 mobile devices. The 4K TV was purchased to improve my photo editing capabilities.
Usually I have a photoshop document on one display, a coding window on another, the resulting page on another monitor, and a style guide or code reference in another window.
On my second virtual desktop I have a console for ssh, one for logs, one for compiling / build errors, and one for general use.
On my third virutal desktop I have work IM, work email, spreadsheets, and OneNote.
On my fourth virtual desktop I have a music player, a browser with forums & news, personal email, and personal IM.
My fifth virtual desktop is reserved for overflow from the other ones.
The mobile devices are for mobile app development and/or for taking with me to meetings. In the case of the Surface Tablet it's for specialized tasks like drawing, sketching ideas, or note taking.
OLD:
2 desktop monitors, 2 USB monitors, 3 phones, 3 tablets, 1 notebook.
NEW:
1 50" desktop display, 2 notebooks, 1 hybrid, 1 tablet
That is indeed a standing desk from IKEA. It is the manual crank one rather than the automatic lift. I love the desk.