There is no feature of a tilt shift lens that cannot be replicated with current high quality bodies, lenses, software, and tripod heads. If you want a TS lens as a way to inspire creativity, go for it. If you think you will create more perfectly sharp images with less fuss, think again.
You can fake tilt DEfocus, but you can't fake tilt focus with a single shot. You also can't fake shift in software with a single shot, and in some cases you can't at all (lenses only go so wide). The best answer is to use whatever tool is necessary for the situation. If you don't have things changing in frame then a pano head + focus stitching makes sense. If things are changing then a T/S is the way to go. If you already own T/S lenses then you can do shift panos, with the trade-off of lack of "un-distorting processing" resolution loss vs "edge of lens coverage" resolution loss. I'd prefer to have T/S lenses AND a pano head. If I could only have one I'd take the T/S lenses - at least you can always get the single shot.
T/S in landscape shots: Personally I use rise on at least 50% of my landscape shots (I shoot a lot of trees). I use tilt less often, but often enough to know I need it. After shooting field view cameras the geared DSLR T/S lenses are pretty quick/easy to use.
T/S adapters - I'm aware of Mirex, Harblei (not available anymore that I can tell except Ebay) and Kipon. There are wide-angle limitations. From what I can tell all have the same issue as the PC-Es, shift + tilt OR rise/fall + swing. Not a big deal to me, as I rarely really NEED to use rise and tilt or rise and shift or tilt and swing (never) at the same time, but an issue for some folks.
Metering T/S shots - metering seems fine using the Nikon PC-Es on a D800e tilted and shifted, however I often still use a dedicated spot meter.