If you're a big and tall rider check out this article on Leonard Zinn's development of a new product line.
Even if you don't want/need a new bike, the article highlights several areas in how they chose parts and designed the bike.
Put another way, for people weighing 300 and more pounds, trying to optimize weight of the bicycle to save a pound is a mistake. Instead, the bicycle needs to be optimized for durability/endurance and safety.
While I don't own a Zinn bike, I've attended talks he's given here in Colorado and have been a long time follower of his bicycle tech Q&A in Velonews.
