I did LAX-LIM-SCL-GIG-SLC-EZE on Lan Chile with a friend in June of this year. No problem getting two seats in F on the days we wanted.
Good airline. Better seats than AA on the 777 or 767-300 (non suite), but not as good as LH,CX,SQ,QF,BA etc..... Since i dont speek spanish and the englis of some of the flight attendant is very limited the communication was sometimes difficult.
I would use them any time again.