Updated Gmail interface has a compose window at the bottom right corner. My initial impression is that it just doesn't feel right because it breaks the standard middle of the screen placement. I got the same feedback from a few other people. The window also cannot be moved or re-sized. Based on the answers below some rationales are consistency across products, ability to access other components (messages, contacts, etc.). How would you redesign this UI by not having the window in the bottom right corner?
closed as not constructive by Rahul♦ Nov 2 '12 at 21:57
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I suggest their third point is the main one here - it allows you to do other things while composing emails - for instance to still be able to view other emails while you're composing one yourself.
After reading the comments I'd hazard that a plausible explanation would be that Google is trying to standardize their interfaces across applications. DAO1 pointed out that the placement is consistent with their chat windows, which makes a lot of sense.
If this is their goal, it would certainly explain this part of the new Gmail interface, although the more interesting question (and perhaps more relevant to this forum) would be to ask whether this change could be implemented in a less confusing way.