Yup. The demo will give you a good idea of what it's all about, but the game really shines in online leagues when you're playing against human opponents. It's something every die hard fantasy baseball player should look into. I actually quit fantasy baseball after I started playing OOTP.
Clay's review of OOTP 2007 is a must read:
http://reviews.operationsports.com/R...?game=ootp2007
If you're not sold yet, take some time to browse through the recent articles our owners have written:
http://www.simgamingnetwork.com/brow...?c=2&styleid=4
And browse through some of the game generated reports that are updated after every sim:
http://www.simgamingnetwork.com/blb/..._100_home.html