I'm thinking about buying a complete upper from J&T, but the Bull Barrel is stainless and chrome-moly lined made by Shaw.  I've heard J&T has a good rep but I'm not sure about ordering a "varmit" barrel that's lined.  ????

Unless you pay the extra $50 on the M4 or A2 models your not getting a chrome lined barrel (I dont know if they do chambers or not). Chrome/moly steel is what the barrel is made of it doesnt mean the barrel is chrome lined. There is a differance.

I have a JT unlined chrome moly barrel on a rifle. Its a nice little tack driver.

Id stay away from SS barrels unless I was into slow fire shooting.

The SS barrels are whats on the SPR rifles. I love my 16" RRA SS barrel. No worries about whether chrome lined or not, and its easy to clean, and more accurate. All this does come at the cost of a little wieght though.
Id stay away from SS barrels that are lined.

The "bull-barrel" kit on their website says it's a stainless steel Shaw barrel.  That won't be lined with anything; it's just stainless.