Was just reading brew your own magazine and they had a write up on open soucree Brewtarget. I use ProMash which has its bugs imo. Will give this one a shot and thought I would share, for free can't hurt: http://sourceforge.net/projects/brewtarget/
The $20 or $25 it costs for Beersmith is well worth it.
Anyone using it on Mac? I downloaded the Mac version and it says that it doesn't work with the version on OS X. I'm 10.6.7 (Snow Leopard) which is the latest.