Most people that own a Model 1 kit, are satisfied. Hard core Colt or Bushmaster people are rarely impressed by a "kit". It all comes down to this. Do you actually get what you pay for? Or is this all a brand-name game?
I think (I am no expert), that there is a point in price where you are no longer achieving significant improvements in quality. Is a standard Bushmaster rifle really $500 better than a standard A2 kit from JT or Model 1? Will it be $500 more reliable? Or last $500 longer? Will the fit and finish be $500 better?
I have read about Colt and Bushmaster. Colt in particular spends more time and money on quality control. Parts, materials and function are all tested and contructed by higher standards. Kits are probably not even tested in any way or form.
I think the Model 1 Kit is fine. I have a decent eye for detail, and I don't see it to be any different from any major brandname makers. After all, these are military style type rifles. For the price, the kits are plenty fine. If you are worried about function, read here a while - colts, bushmasters, armalites everything has failed to funciton or has had something break. Nothing is perfect.
Get the kit and save the money for other things. If something breaks, replace it - isn't that one of hte best aspects of the AR? Easy to work on. If you are ultimately disgusted with with kit, trade it or sell it towards a brand-name maker and try that route.