Who upgraded from a 17-40 f4L to a TSE 17 f4L ?

I wonder is the 17mm tilt'n'shift really a big upgrade?
In past I tested 16-35II but it was no real upgrade, just a stop faster.

So corners of the TSE are sharper + you can tilt'n'shift to have straight buildings,... I just did some corrections of my 17-40 with LR4, but to straighten you have to cut a piece of the pic.
Anyone has the TSE and is extremely positive of this lens, maybe the ideal UWA on FF ?

I did, although I still have the 17-40 for the times I want a zoom, AF or weathersealing.

The 17-40 isn't in the same league, not even close. It's like comparing the 18-55 kit with an L prime. The kit lens is decent and does a good job for the price but.......
So yes, it's a chunk of change, but the difference is significant. Also the difference in IQ between applying shift and correcting in PP is significant, especially with detailed subjects like trees.

That's not to say the TSE is perfect. It's still UWA and at large shift or tilt the corners benefit from stopping down, especially for very close foregrounds. To get the best from this lens, when I need a very large DOF I often focus stack if I can.

Bottom line though: if you're looking for something significantly sharper than the 17-40 at the wide end and are not cost-conscious, you should like the TSE.

Upgraded to the Zeiss 21mm.
Difference is huge.