We were just given computer upgrades and I went to install the latest HEC-RAS version (4.1.0) and noticed on the Corps software page that this version has a "RAS-Mapper". A tech here looked at it and HEC-RAS it appears to take a DEM Float file (.flt) (convert TIN > DEM flt in ArcGIS) and use that to plot flood extents. This almost looks like a work-around from GeoRAS. With the cost of the ESRI software licensing, I can see why the Corps might move some of this functionality into HEC-RAS.
I'm not driven be a project to check out the RAS Mapper, maybe some of you are at that point and could report.