I like having the front firing speakers since my finger sometimes covers the speaker when I hold the phone in landscape with one hand. With the bottom speaker, I have to kind of "cup" the speaker to "direct" the sound frontwards. The sound isn't bad, but I do prefer the front firing speakers for this reason.
On calls, with Verizon HD calling, it sounds amazing. With regular calls, it sounds pretty good usually, but if I'm outside, I often find myself selecting the "Turn on extra volume" option.