Upload & Sell: Off
I just picked up a Tiffen 87 IR filter (out of personal interest due to this thread). This is a "Wratten #87" filter, which is equivalent to Schott RG780 glass (also available as the Heliopan RG780 (87) filter), a 780nm long-pass filter --- so a considerably deeper IR cut than the Hoya R72 (720nm long-pass). On an un-modified 5D, the result is almost monochromatic, with a closer balance between the RGB channels than the R72 (Aperture.app is capable of setting a white balance, at T=2000K, tint=-91 --- weaker IR filters produce results out-of-range for this setting). There is significant color shift towards the corners, probably due to angular dependence in IR transmission of the camera sensor package. You also really get the "bright white glowing foliage" look typical of deeper-IR shots. This is at the expense of further reduced light: in near-maximum sunlight, I needed 20s at f8, ISO400 for this shot:
With my B+W 093 filter, an even deeper 830nm long-pass, yet another stop of light is required for equivalent exposure (now 20s at f8, ISO800). The results are basically completely monochromatic, including eliminating the color shift:
Once desaturated to pure monochrome, the 780nm long-pass results on an unmodified 5D are nearly indistinguishable from the 830nm long-pass, at 1 stop faster exposure, so this is probably the best filter choice to produce the "stronger IR cut"-look monochrome images.
With a modified camera, one could get much more usable shutter speeds (greggn's example above took 1/125s @ ISO400 in similar outdoor sunlight to what took 20s @ ISO800 on my unconverted camera --- 12 stops faster!), and also likely less color vignetting (from the angular dependence of the removed IR-blocking filter).