Well, yeah, the Eurostile cabin is boring and i just hate it, but you can still find many 767 operated intra-southam routes. Just flew SCL-MVD on sunday on the 767, with the Premium Business and the new economy seats.
Plus, most aircraft have the Business Express Cabin, it just ain't showing up in some routes. Honestly, I don't know why, but every A318, and most A319 and A320 have business express cabins. Also, a limited number of A320s still have full business cabins (those planes do Ecuador-Argentina runs mostly, and some Santiago based international routes) but those are being phased out/converted to the new cabins with leather seats. No domestic flights have them, though. It'll be interesting to see if LAN decides to make them available in Domestic Argentina flights (since the competition offers them, with somewhat good results)
Maybe if you elaborated on what flights you are taking I could help you more.