I could say bottom posting is stupid -- why force me to reread all the previous content and have to search for the new content? When you're talking with someone, you don't repeat the entire previous conversation before starting your new entry into the conversation. Which is what bottom posting does.
The biggest problem I have with top posting is that too many people don't bother to trim ANY of the message they are replying to. But, the same problem exists with bottom posting. I don't mind bottom posting if all that is repeated is a line or two. But when it's 2 or 3 pages of text? Forget it.
In general, I prefer top-posting, simply because I want to get to the new content right away. In many cases, I am already reading the thread of messages, so I don't really need things to be repeated to me before a response is made.
About the only time I do a bottom posting style is when I have things interspersed. But in that case, it's to address things point-by-point, as a Q&A type message. So, bottom posting on each point. But the repeated text is usually VERY short.
What makes both top-posting and bottom-posting bad is lack of effort on the part of the message writer. They are just too lazy to trim properly, so way too much extra garbage just gets in the way. And this Google change just encourages that.