This is a question that has been talked about a lot in this forum.
For some, Crossfeed is a amazing feature which they can't live without, while others find the extra processing unnecessary, and intrusive.
And you can guess I am a fan. I like having it around, and the effectiveness of the Headroom's version (even compared to other versions like in Meier's amps) steers me toward their products. I switch it off for certain recordings, but for some older recordings with exaggerated stereo effect becomes much more tolerable when listening to headphones. It really does bridge some of the gap between the "blobs in your head" feeling with headphones compared to speaker listening. The effect is still pretty subtle overall, so don't expect it to change the sound stage to Carnagie Hall like on some Home Theater receivers try to do.
My take on it is: Headroom makes solid sounding products, crossfeed or not, they are worth considering. Nothing can beat trying it for yourself in the comfort of your own home with their 30 day guaranty. I'd buy their products based on solid design itself, but the Crossfeed sweetens the deal.
The Crossfeed in the latest Headroom products is noticeably more transparent sounding than the earlier ones. I just got a Total Bithead and the crossfeed has less intrusive effect than my Airhead.