Not entirely. The big difference here is that you only have one, integrated architecture to maintain. So that means less operational complexity, smoother “scalability” of your infrastructure, tighter integration between DB & Search. Also, we added stuff like queries across several indices, typed queries, etc.
Hm, as far as I understand multiple-index (core) search has been implemented in Solr 1.3?
Sharded search is not new. Solr, elastic-search, and Riak do it as well. The difference here is that we've built the Search on top of the BigCouch map-reduce view model. Views are calculated post commit so there are no data insertion locks. Multiple copies of each shard exist for fault-tolerance. Also, multiple map-reduce analytics passes can be used as input to the search.