I own the 24mm PC-e and the 85mm PC-e. For product photography (something I admittedly don't do a lot of), I love the 85mm. For landscape photography, I find myself using the 24mm almost exclusively. Here's an example of a scene taken with both lenses (on different days with vastly different light):
Here's the 24mm:
Glass Pedestrian Bridge and Aquarium at Sunset 24mm by
Trevarthan, on Flickr
And here's the 85mm:
Glass Pedestrian Bridge (person merged out) by
Trevarthan, on Flickr
Let me be clear: I'm absolutely NOT interested in the miniature effect. I see a lot of reviews around the net written by people who seems to think the only reason to buy a tilt shift lens is the miniature effect. I view the miniature effect a lot like over processed HDR: meh. I would use this lens to place the focal plane in line with my subject at f5.6, expanding what is in focus, not isolating it. I'll be using this lens exclusively on a tripod with a D810 and live view. I don't understand why everyone wants to hand hold these things.
Anyway, I picked these two focal lengths back in 2010 because I loved the way they lied to me. 24mm is wide and exaggerates the foreground and expands space. 85mm is telephoto and exaggerates the background, compressing space. 45mm is just normal. I've found a few scenes recently where I can't take the shot without 45mm. 24mm is too wide to be interesting, and with 85mm I don't have enough room. Sitting here typing, I realize maybe I could do an 85mm panorama, but the light changes so fast after sunset and the exposures are so long, I'm not sure how that would work.
I mostly want to take cityscapes and landscapes. Should I bite the bullet and buy the 45mm PC-e, or not? What's your opinion?