Yes I've tried both hardware and software crossfeeds. I'd usually rather have crossfeed than not. To me crossfeed needs something more though. A large and forward soundstage helps in that circumstance. Chances are if I had some HD800s crossfeed would be enough.
For me, Dolby Headphone provides an excellent psycoacoustic representation of stereo speakers in a way that simple crossfeed simply can't, even with headphones with a small and central native soundstage. I percieve pracitally the same 3D soundstage when using DH1 (with mapping as described) as when using nearfield monitors. I like DH3 for very 'dry', closed miked, studio recordings but it can make a bit of a mess of live recordings with some natural ambience. For some reason I've never got on quite so well with DH2. When using headphones with good synergy (Goldring DR150 or NS1000, Senheiser HD580 or HD600 all work well) with Dolby Headphone I perceive a singer, for example, as being out in front of me and not in my head.
Of course, it wouldn't work like that for everyone. I just happen to be extremely suited to the Dolby Headphone algorithm (for me no other HRTF based headphone processing comes close).
It's not really out of choice but I live in a terraced house and have two small children so a lot of my listening these days is via headphones.
I'd love to try a Smyth Realiser, properly calibrated, but don't fancy spending that much on headphone audio any time soon.