My preference is to go with etcd over search. Currently we're using it for all other host discovery & it works exceedingly well.  So for no other reason that just consistencies sake I think its a good idea.  It also allows systems outside of chef to access this information too.  Its a lot easier to query etcd than to query solr.  Search is expensive, more so as the  number of nodes grow so this will improve performance long run.  I can help if you've got any questions.