We ran a number of tests to see how many reads per second we could get from MySQL Cluster. We used a modified version of flexAsynch (as shown in previous blog), where each record read was 100 bytes in size.
With a cluster of 4 data nodes operating on 2 machines we were able to process 1.15M reads per second. On a cluster consisting of 8 data nodes executing on 4 machines we were able to process 2.13M reads per second. On a 16-data node cluster with 8 machines used for data nodes, we were able to process 4.33M reads per second and finally a cluster with 32 data nodes distributed on 16 machines we executed 6.82M reads per second. The tests were run on MySQL Cluster 7.1, we're confident that similar numbers can be achieved with MySQL Cluster 7.0 and also with the new beta version MySQL Cluster 7.2.
This benchmark will give you a good idea what can be achieved with direct usage of the NDB API, and using other APIs like Cluster/J, mod-ndb, NDB-memcached.