I have really enjoyed Five in a Row. It is very easy to use, and provides a nice instant lesson for someone who doesn't always have time to plan. It also provides about 12 different lessons for any given book, so you can choose which ones fit your goals and your beliefs. I have been able to check it out of our public library - see if your has it, too. Then you can decide whether you want to use it without spending the money.
Volumes 1, 2, and 3 will get you through about 1 to 1-1/2 academic years.
About the Christian component - Five in a Row doesn't contain specific Christian elements, but it definately "feels" Christian to me. By that I mean that optional lessons include discussion of morality in some stories. I guess my perspective is that morality is a good thing to discuss with children, but I wouldn't expect to see such lessons in more secular homeschooling programs. Some of the stories are Christian in content (Clown of God, for example), but could easily be taught with a "this is just a story" or "this is a story that some people believe to be true" approach. I should add that the Five in a Row lessons for Clown of God make no reference to god or religious belief - it is treated strictly as a story.
We are only partway through volume 1, so I can't speak to the issue of stereotyping very well, but the stories we have read so far span a number of ethnicities and genders. Many of the books are older, but for our family they are classics that I would tend to read anyway. And she also includes some topics (Who Owns the Sun is about slavery) that I would not have known how to introduce to a 5-year-old. On the other hand, no books with lesbian or gay characters are included in the series, so it is by no means an inclusive curriculum. It is definately very mainstream in its approach, but that doesn't prevent me from using it as a springboard for the kinds of issues I would like to discuss. For example, I thought the grandmother in Cranberry Thanksgiving was very selfish, and so I included a discussion of her character on our social studies:human relationships lesson day. You might also use this book to introduce Native American perspectives on Thanksgiving.
What I have most liked about Five in a Row is that it gives me ideas for how to approach homeschooling with other stories as well. I preview the stories at the library and only use those that are consistent with something I want to teach. Or sometimes I'll get a different book, but use the Five in a Row approach to come up with my own lessons.