Mac, Roy,
I don't like ipe because I've found that you can get a flaw in the wood that's all but impossible to see until the bow is done. I think when they fall those giant trees, the uneven ground or other trees they land on can cause fret-like damage that's all but invisible. If you get one in your board, every bow you make from that board will break in the same place.
Of course if you get a good ipe board, the material is flipping awesome. If I ever build with ipe again, I plan to examine the wood very carefully after scraping to a glossy finish before I glue up the bow. After that, if I do get a failure, I'm throwing the whole board away and using a new board on the next bow. It's too demoralizing to have bows just keep breaking. Especially in the same spot.