OCWEN Shared Appreciation Mortgage

My home is about $30k underwater. I noted that OCWEN is offering a SAM (Shared Appreciation Mortgage). I am looking for any direction/experience I can get on this type of mortgage. I have never been late with a payment, my credit it good. Could this mortgage effect my credit score? Would I need to pay the IRS taxes on the "forgiven" amount asap? Any downsides to this mortgage? I do understand the shared value in equity idea should the property rise. Thank you.