Here's my history. NEC 27" monitor (lots of real estate). My first tablet was an Intuos 4 medium. What I discovered quickly is that the pad is very much too large, even for "fine work" with the brush tool. I ended up rescaling to an area that (quite by accident) is about exactly the size of the "small" Intuos tablets. Lesson learned. There's more to be gained by changing the image magnification than there is in having a large pad where it takes a lot of hand/pen movement.
BUT WAIT! I then read about the Intuos 5, that can be used wirelessly with an extra little module from Wacom. I bought the small size. REVOLUTION. The 5 models use "gestures" so that in addition to the pen / brush you also have what amounts to a huge "mouse pad." This eliminates for me the back and forth from mouse for "some things" and pen for brushes. I couldn't live w/o my I-5 now, and I wasn't particularly a fan of the I-4 due to its limited used for fine brush work w/ the adjustment brushes.
When I now add the greater range of controls available in LR4 "as brushes" (e.g. selective noise reduction) I find the I-5 being used even more than previously. Mind you, all of this commentary coming from a "non-tablet" guy in general.
Before you pull the trigger on an I-4, be sure to check out the 5. As for the buttons, another feature of the 5 that I like better is that when you hover/light press a button (all customizable, by the way for almost any key-stroke / function in LR) you get an "on screen display" of what action that button will produce if you actually push it. At first I thought the lack of LCD labels on the buttons of the 5 a "take away" from the 4 model, but in actual use keeping my eye on the monitor turns out to be way better.