I haven't looked at any of the underlying research but I found the following claims to be very interesting:
In the end, however, much of what my research uncovered was inconsistent with Strauss and Howe’s theories. At least in terms of psychological differences, generations do not occur in cycles; instead, the changes are primarily linear, with each generation taking the previous generations’ traits to the next level. There is no sudden shift in personality for someone born before or after 1982 (Strauss and Howe’s cutoff for what they call the “Millennial” generation). Thus generational labels such as Boomers, Xers, and GenY are of limited use. What’s more important is the number of birth years separating two people – e.g, 20 years or 40 years. Although I occasionally use generational labels (such as Generation Me or GenMe to describe today’s young people), I primarily rely on labels such as “older” and “younger” generations; those in the middle in terms of age (today, the GenXers in their 30s and 40s) will typically fall in the middle in terms of traits and attitudes.
One particular implication is that individualism and indeed narcissism have been increasing steadily with each generation. I find that the most plausible models of intergenerational learning support the author's "linear accretion" view rather than cycles of rebellion and counterreaction. There is a niche effect for siblings, but I think less of such an effect for generations per se.
Hat tip goes to BPS Research Digest.