You're absolutely right; you can simulate the effect in Photoshop -- with a little practice.
I think it all comes down to what's most important to you: post production time or minor equipment expenses.
I prefer to record the images as close to the final product as possible. That's one of the reasons I like digital cameras so much -- they allow me to preview the picture while I'm still on location. Then, I like to upload the images to iPhoto and begin using them right away without major adjustments.
But I realize that others enjoy post production as much, or sometimes even more, than the actual shooting. For those folks I still recommend that you record the best image possible in the camera, but you can save on some filters and other accessories thanks to the power of modern image editors.
BTW: One of the reasons I mention using sunglasses for a polarizer is for those who can't use, or don't want to buy filters.
Thanks for you thoughts :)