Code Monkey's PCGEN, I would have to give the nod to Red Blade. User friendly, just as flexible as PCGEN and stable. Downside is that it prints in HTML so it uses your browser.
PCGEN prints its own files, but still has fundamental bugs that after two hours I could not fix, such as will not allow paladins Weapons Focus. It also works hard at being user unfriendly. I want to make characters, not learn another language.
Red Blade has it's share of quirks, but because it's easier to work with I give it the nod over PCGEN.