If you shoot a lot or just don't clean like you should then a chrome or nitro barrel will last longer. Every barrel manufacturer turns out good and bad barrels and it's just luck of the draw if you get a good one or bad one when it comes to production grade barrels but, some manufacturers have better quality control and then some better builders may catch problem barrels so you will have better luck with reputable company. Some companies could be selling bicycle parts for all they care they just move barrels from one box to another and ship so all the bad barrels are passed along to the consumer and they have a bad rep because of it. There are 3-4 barrel manufacturers that make most of the barrels for all of the companies that sell AR-15s. The cheapest unlined barrels are just cheap and I doubt anyone inspects anything.
With the warnings in place and understanding you don't plan to shoot much and will clean the rifle after range trips I don't think an unlined barrel is a deal killer if you buy from a reputable company.
ETA- Someone over on arfcom shot over 50,000 rounds(cost of ammo apx $15000) through a SS barrel before it failed(key holed a bullet) and CM will outlast stainless as long as it is cleaned regularly. Typical accurate(2-3MOA) life span for CM or stainless is apx 8000 rounds, chrome and Nitro Carburized barrels can double that according to some shooting carbine courses on a regular basis.
Last edited by Constructor; 03-29-2010 at 12:18..