Gee, you're brave opening this can of worms again:
link
In this there was a link to this page, which is quite good:
Horsehead page
The general consensus is that you need a good quality instrument, you need the Horsehead near the zenith and you need good steady and transparent skies. Aperture is not crucial to some observers. I found having a photo that I cut out of a magazine and laminated nearby to check out the starfield was very helpful as well. And get zeta Orionis out of the field, it's blinding!