None of us here at Probe have any cautions or reservations about it.
Personally, I think it has become so popular because Rick Warren has taken “Basic Christian Living” principles and put them all in one place, in a highly accessible format. One of the best things about the book is its first sentence: “It’s not about you.” So his starting point is that the Christian life, the purpose-driven life, is about giving glory to God. It’s not about personal fulfillment or self-actualization—it’s all about God. That puts everything else into proper perspective.
The fact that this book appeals to both believers and unbelievers is exciting to me, because we are all hungry for truth and this book has it. It is steeped through and through with Scripture, and it’s well written.