Bazarov is supposed to be immature and obnoxious because...well...he's a kid. Sure, the ages aren't maybe the same as today's "frustrated youth", but the whole concept of "teen angst" is pretty obvious.

There is an inter-generational conflict between children of the Thirties and children of the Fifties that mirrors the same conflict a century (and two decades) later. The older generation was an optimistic one that thought it could change things and had a sense of idealism, whereas the younger generation was disillusioned and discouraged (and often nihilist). The change that took place in Russia to disillusion people was the increasingly despotic reign of Nicholas I, which set Russia back immensely and ruined many of the quiet reforms of Catherine the Great and Alexander I. The Decembrists would die in Siberia, and people who spoke up on their behalf later (like Pushkin) were exiled and silenced, and censorship steadily increased.

Pavel Petrovich likes to still think of himself as a "rebel", but he often looks a bit silly, much like a 1960s ex-hippie who is still trying to "fight the system, man". Bazarov's nihilism seems to stem as much from his feeling of powerlessness (there is no way to fight the system in reality) as it does from his youth and desire to reject the older generation's value system.

I didn't see Bazarov's death as suicide. I saw it as him attempting to pretend to be a nihilist even though he no longer is to seem brave, when in fact he wants to live and love. It was a profoundly sad ending to the book, and I think I felt more sorry for Bazarov than for any Dostoevsky character who dies (maybe excepting Elena/Nelli from The Insulted and Humiliated), perhaps precisely BECAUSE I too hated him at the beginning.