I have a Terrafirma on the front of my Gems 4.6 - just a couple of points as a result of a recent removal (from a body lift) - note the car came to me with it fitted.
Mine is obviously a lash up of a Discovery 2 - they may be different/better now, but check - some of the structural strength is questionable on mine.
Mine only picks up on the four front bolts - there's no pick up further back so as a winch bumper its more decorative than functional - if it was stressed, the chassis crumple zones would inevitably be stretched or the bumper would let go - there's a possibility of air bag deployment (I would guess) as a result of exuberant use.
Mounting hole alignment with chassis mounts is poor - bolts needed hammering home as things we not in good alignment.
Like I say, mine is a few years old so maybe they're better now, but for me its a bit "pretend" - I would have liked to have seen extra mounts further back on the chassis to bridge the crumple zones, and the strength of the bumper outers to be improved - mine bends real easy (helps if you have a friend with a winch to pull it straight once in a while)
As a point of note, make sure the bits covered by the original bumper are adequately covered - check washer bottle and A/C pipes and drier - I had to make "cheeks" for mine as these bits were really exposed and prone to impact and mud - when you fit it, I guess you'll loose the front driving/fog lights - pull the connectors out of the way and heat shrink them.
I have a front one on my discovery 2 and it is very good, fitted fine. We recently installed a P38 one on a diesel model, there was a bit of pushing and knocking but it fitted soon enough. The paint could be a bit better. it certainly is in both cases much more functional than the original with the silly plastic skirt