Ben writes (emphasis his):
System.Web.MVC will reach an audience that MonoRail doesn’t:
The corporate giant who already swallowed the pill and will do anything
that Microsoft pushes, good or bad. And a lot of consultants work firmly in this space.
That's probably the call when it comes to MVC on IIS in the large. I think, however, MonoRail will remain a viable option for smaller or more edgy shops simply due to the agility the open source approach provides. Namely: Castle can release more often and quicker and it's got a number of smart programmers on the job already. Think of it as the Paul Graham effect.
The determining factor will be where the developer community goes with this. MVC has the makings of a good trade post. Then again I'm sitting here wondering does it really matter?
I'd choose (if I had the choice) the edge and as it sits right now - for web applications - I'm leaning toward and investing personal time in learning Rails. DLR/MVC or DLR/IronRuby somewhat weigh on my personal judgment, but then I think about the vast array of overwhelmingly free and overwhelmingly excellent tools available to the Rubyist and Rails-head: autotest, rspec, acts_as_state_machine, acts_as_your_10th_grade_geometry_teacher_mr_moore...
I don't know. For me it seems - political arguments aside - if you want to be out there on the (sometimes bleeding) edge you'll always be where the rockstar programmers are.