I ran a lockrite in my IFS front end from about mid '04-mid'09 with no problems at all.  Didn't have a difficulty steering when offroad, and when driving in the snow on the road, didn't have any trouble either.  It was definitely a great mod that allowed me to keep my IFS a lot longer than most people do when using their trucks predominately offroad. 

I'd say go for it


FYI, my setup was 5.29s front and rear, 37 MTRs then 35 BFG MTs, detroit rear, lockrite front, and from '06 or so on, duals.  When I went to my SA, the lockrite was working fine, and traded to a buddy of mine, who used it with no problem.