An Objectivist friend of mine recommended to me a book on Buddhism entitled Wake Up to Your Life by Ken McLeod. So far I've read only the first two chapters but I must admit I find myself nonplussed. McLeod presents the Buddha's fundamental insight as the centrality of suffering in human life. That may have been true 2500 years ago on the Indian subcontinent, but in today's world that claim simply does not resonate, at least for me. While I find some Buddhist methods for living to be rather attractive -- living in the moment, cultivating clear awareness, understanding without (necessarily) judging -- I feel that the foundation of Buddhist thinking is shaky because of its extreme focus on suffering.
Nietzsche too questions Buddhist foundations, not because he thinks life is without suffering but because he doesn't think suffering is necessarily bad or something to avoid ("What doesn't kill me makes me stronger!"). For Nietzsche, philosophies such as Buddhism, Christianity, and in the end even Epicureanism (whose founder he much admired), are based on fear and the avoidance of pain and suffering, and thus are weak-willed forms of pessimism. They are focused on negation (nirvana, transcendence, ataraxia) rather than the strong-willed, positive pursuit of individual flourishing and value-creation.
But these are early thoughts on the matter. I'll post more as I read more.