Is RAM Latency a True Key Feature for Performance?

MacBooks and iMacs are currently shipping with 5-5-5 DDRII modules (CL-5). TT Hardware (in French) carried out a test on PC to evaluate the impact of faster SO-DIMM modules (4-4-4, CL4) on performance levels.
The test platform being the Intel Santa Rosa, results can be extrapolated to Macs.
The maximal measured performance game is 5%, and the overall gain is 2.38%, in other words, marginal; and the premium cost could simply allow you double the amount of 5-5-5 modules for the same price.