I used Breakthrough 2 by Miles Craven for one of my advanced conversation classes last semester. Overall, I was very happy with it and would be happy using it again. I liked it for the following reasons:
-a good number of communicative type activities for use by partners.
-the grammar teaching concepts were manageable chunks but not too easy. Exercises were helpful.
-an adequate amount of material on each page. Not too much, so that you get overwhelmed but no wasted pages either, as in some textbooks.
My friend used this same book for all her freshman English classes here in Korea with good results as well.