The disk io was pretty low. It is serial get/update/delete (as I mentioned earlier). I even tried moving the data dirs to ramdisk (was plenty of ram), but it didn't help much at all. i/o was certainly not the problem.
It very well could be a configuration issue. I am still trying a few things to see if I can get an improvement.
Interesting. I can vouch for the speed of leveldb on a five node cluster - I'm using it in our startup on 5 dedicated machines with around 12GB of RAM, running on FreeBSD. Riak version is 1.1.4; Riak 1.2 is supposed to have a lot of leveldb refinements.
It very well could be a configuration issue. I am still trying a few things to see if I can get an improvement.