Oh yeah forgot to mention, we've got a pretty cool system for the contact pictures! The contact picture is only used for the first of a group of consecutive messages. But it's sticky, which means that when the picture would scroll out of view it's fixed to the top of the screen, and the "arrow" (only 1 arrow per group of consecutive messages) sticks to the picture and jumps to the closest bubble.
It's a bit hard to explain, but it looks nice and clean, and makes it fun to scroll through a long list of messages :)
Also, we've looked at a lot of other IMs and they've all got their good and bad elements. In gTalk's case, we think the text is displayed nicely, but the graphics around it get a little awkward at times.
It works great for 1-3 lines of text (even though 1 looks a bit awkward too). But when the number of lines is high enough so that the text comes lower than the bottom of the picture, the part under the picture is just filled with grey. I know it's supposed to represent the BG but it just comes of as an equally important element since the pieces of BG aren't connected. That's one of the things we're trying to avoid, and a big reason why we're not just copying stock.
Thanks for the feedback!