Funny this topic came up. After I got my 5D2, I packed up the 5Dc for sale. But then, decided to sit on the sale idea.
I don't know if anyone here has compared the IR images from DSLRs with those using Kodak HIE film. DSLR IR images are just too smooth. Kodak HIE is special in other ways, too but I cannot see myself scanning films a lot. Besides, after selling my 1v a few years ago, I'd need to buy another EOS-1x to use IR films. Well, as a possible solution, this morning I ordered a 77mm R72 filter to use my 17-40 + 5Dc. I previously used a 58 mm filter with a 24 f/2.8 but none of my current lenses can use it anymore. 24 f/2.8 is not actually a great lens for IR but people report 17-40 is. I'm hoping at ISO 1600 with my 5Dc I can get some grainy effect as I used to get with HIE.
So there, an excuse to recommission my 5Dc, hence keeping it!