NHibernate's Mapping by Code - first impressions

NHibernate's 3.2 new mapping-by-code feature allows to completely remove XML mappings from NHibernate's pipeline. I'm pretty used to using Fluent NHibernate, but I always think of it as the only replacement for plain hbm.xml mappings, that are just too clumsy and too verbose. I like FNH's fluency and clarity, but I think it's far from being ideal solution. Mapping by Code from NH 3.2 seems to be promising alternative.