Bitcask is specifically designed around not doing random I/O, particularly for writes. A bitcask back end is essentially a gigantic sequential transaction log.

While SSDs will undoubtedly be faster that spinning disk, LevelDB is designed to address slow random writes by batching and writing sequentially.

That would be true except each vnode (by default 64!) has its own backend database. That means with 4 physical nodes each one gets 16 leveldb/bitcask/whatever database backends.

LevelDB's write batching and caching is completely void when thats considered in many circumstances.

Its something that I think Basho should consider changing. Its a trade off of fault tolerance or performance, and I would personally love to see riak go a lot faster.