Bill described it very well, so I won't bother repeating his wisdom. I will add, a few things though.
First, a lens that tilts and shifts can be very useful for landscape photography, but they are not always appropriate or even necessary. It all depends on each individual scene. Conversely, there are times they are crucial, especially when working with lenses that are not wide angle. It all depends on the scene. For example, in one of Michael's videos he spent time with Clyde Butcher in the Everglades and while on a shoot asked Clyde if he was going to tilt his lens. His response was that the vertical trees made it impossible to use tilt. In another of video, Michael used swing (tilting horizontally) to get a row of Redwood trees all in focus; an image that would not have worked with a standard lens. (apologies for the multiple Michael references, but it is HIS site, after all).
As you're just starting out, it might be best to wait a bit and see how your photography develops and how happy you are with the results. No sense in rushing off to spend a couple of grand on a single lens unless, of course, the letters "M.D." follow your name
I am a Nikon user and I have both the 24 and 45. The 45 is my workhorse and accounts for 3/4 of my work. It's ability to tilt is of utmost importance in much of my landscape work and I would have hard time living without it. The 24 is very useful, as well, but I don't use the tilt near as much as the 45.
One benefit of these lenses is their amazing image quality. As the image circle is much larger than the sensor (to allow for shifting), most of the sensor is in the sweet spot of the lens, making these some of the sharpest OEM lenses I have ever used. They are so good, in fact, that I have dismissed my standard lenses of similar length.