I've seen this kit too, and all of the research I have seen suggests that it is probably an improvement over the Gulstrand mod, but man, it's not cheap! I chose to go with their upper control arms, and lower themper the Gulstrand method. The arms are really nice, and they adjust for caster as well, which is really nice. Haven't driven the car yet, so my info here is useless, sorry.
One thing I have heard about the brakes is that Wilwoods tend to be noisy, rattling, etc. I had a "pro street" kit on a 72 Chevelle a couple years back, and I did not experience this, but have heard this complaint from several sources. In addition, Wilwood just came out with some newer kits that clearly state improvements that reduce the noise issues, so there must be something to it.
I think that if I was thinking about dropping that much money, I would probably consider an aftermarket front subframe, with rack, etc. $4k is alot of money, but then again, I'll have spent about $2500 on mine with brakes, so maybe it isn't too outrageous. I guess it comes down to "how well do you want it to work?" I am confident the the Gulstrand/control arm package will be all I need for aggressive street fun.
69 SS, Stroker 489, Tremec TKO, Tight Road Suspension