Based on what you have said, it sounds like the TS-E 17mm is the right choice. Just one question you probably know the answer to: Is the TS-E weather sealed? With the sliding surfaces it would seem difficult to seal. If it is not fully sealed, then that would cause me to rethink that decision (what is the likelihood that a non-sealed lens is going to damage my camera of an expensive lens?). If it sealed, then easier choice.

I would love to have the TS-E, but there is one thing that would push me more toward the 24 mm before the 17mm (I know that is not your problem)... and that is the filter issue. I understand your fix for the ND filter, but with landscapes - living without and adjustable GND would make the choice tough. Is there a solution for that?

Pat