Since most of the money I've made from photography has come from architectural and construction subjects, apart from large format I've used a lot of shift lenses. I still have a Canon 35TS from the 70's, a Nikkor 35/2.8, a Nikkor 28/3.5 which is now used on a 28/220 Roundshot, a Mamiya 50/4 for 645, and the Canon 17/4, 24/3.5 II and 90/2.8 TS-E's. Also my 150 Noblex has a shift lens. The 17 and 24 Canons prove that Canon can produce excellent wide angles, contrary to previous evidence.
Over the years I've used all shift lenses made, I think except the Schneider for medium format and the 35 for the Contax. Most were excellent, but a few didn't make it. The 28 Pentax, for example had a rather large amount of distortion, which is totally unacceptabe in a lens of this type. Until the recent 17 and 24 Canons and the 24 Nikkor came out, the best lens optically was the old Canon 35TS. I used that one on 35mm and a home made medium format, an it was the best mf lens I had for a while, although awkward to use. The 35/2.8 Nikkor, 35 TS Canon and the 50/4 Mamiya don't see much use now, but the others are employed regularly.
There is no way to digitally simulate the image of the 17 Canon with anywhere near the quality with any other setup, and to a lesser extent that also applies to the new 24. And if you need tilt, you can't really do without lenses like the 90/2.8.
Henning