your gonna catch cracks from some members about searching but i'll help save you the trouble. i too was looking at the zone 4" lift and heres what i found.
there are a couple of guys running them and loving it (apollo is one of them..search for his build thread). from what i've read many of their kits in the past had problems, but now have all been resolved. for those who do decided on purchasing zone, they ended up ordering a much beefier adjustable track bar, some even purchased better control arms that are adjustable. i cant speak of experience cause i dont have this kit, but from my own research, those who do have them love them with no complaints (they just ordered what i stated above).
of course, with 4" lift you increase the chance of DW and if you dont have a u joint shaft, at that height it is recommended. thats why for my usage, i think the IRO 3" kit is perfect for my use.
as far as the "cheap" lift kits go, its one of the better ones. i would have a little money set aside incase you find you need some extra pieces, such as adjustable upper control arms or new tie-rod ends. ever jeep is different due to age, condition, etc so its hard to say if you'll need anyhing else. plenty of people run the kit with just what was included. as with anything in life though, you get what you pay for. its not a bad kit, but there are better (and more $$) ones out there.
2000 White V8 WJ LSR-6in-35's-LA's-242HD-Warn [B]SOLD and missed very badly[/B]
06 GTO - BC Coilovers, JBA Catless mids, Svede Intake
different track bar now that is beefy. It is actually the same size as my Brothers JKS. or right abouts.
Alright, that's good news. I have been looking really hard at the zone 4", and even talked to the Vendor here on the forums to get free shipping. I think since they've improved the track bar, that it will be a great match for my WJ.