The current craze is unbleached flour. There's nothing wrong with it -- I use it myself -- but when it comes to baking, whether the flour is unbleached or not is not the crucial issue.
The protein content is.
The protein in wheat flour (and only wheat flour) has a unique property. As you handle it, the strands of protein connect, forming something rather like a net. It is this net which traps the gas and causes the product to rise. Conversely, the more the net is developed, the chewier the result (think of cakes and breads as opposite ends of a spectrum).
To get the best results, you need to use the protein content that is most appropriate to the product. For example, if you're making bread, you want a high protein content flour. If your making cake, you want a tender, delicate crumb, so you want a low protein content flour.
Flour in the United States is rated by protein content into four categories: cake flour (8-9% protein), pastry flour (10% protein), all-purpose flour (11-12% protein), and bread flour (13-14% protein). Cake, all-purpose, and bread flour are available in almost every supermarket. Pastry flour is often hard to come by, so mix half cake and half all-purpose flour.
Use the right flour, and you can taste the difference. Cake flour will give you the most delicate crumb. Pastry flour (or a half-and-half mix of cake and all-purpose) will give you a more tender Danish pastry. And bread flour will give you a higher rise (you can buy gluten (wheat protein) in the baking section, and add it to bread flour (1 T. to 1 c.) to give you an even higher rising bread).
Yes, you can use all-purpose for everything -- that's why it's called that. But it won't give you the best results. Only using the ideal flour will do that.