Per Tom Lane's suggestion, I increased the pgbench
scale factor to be equal to the max number of clients
in each test run.
Attached sample graph shows 1 - 10 clients,
100-500 transactions per client, with scale
factor=10 for all runs.
There is still a average 9% improvement in 7.4b2
transaction rates over 7.3.4. For low number
of clients (1 - 3) performance was almost the
same. For higher numbers of clients, the 7.4
advantage was often in the 15-25% range. Other
tests with scale factor == number of clients and
other pertubations gave similar results.
7.4 is almost always faster than 7.3.4.
Mind you now, I am *not* complaining.