I've done two divisions in my Yahoo! league for a few years now. I liked the idea, but like people have mentioned, it doesn't really matter if you can't tailor the schedule, which Yahoo! does not allow....at least not that I can see. So, it isn't a major difference except the division winners get byes in the playoffs and maybe a little prize if you go that route.
10 team H2H Yahoo League. Two divisions, 1 win.
HR, AVG, RBI, SB, OBP, K, TB
IP, W, S, WHIP, ERA, K, HLD