About the last seen time...
If you don't want to send out that many requests... why not delay the queries or do multiple smaller batches? How does the original client handle this?
I find it NOT intuitive at all having to open a user's info all the time in order to see the time. (What about doing that when opening the chat window?)
For some reason some user's time isn't updated although they were online whilst my miranda was open, manually querying the last seen time proofs this.
Also I'd like to see the full size profile pics back too, please!
On more thing:
Didn't you implement the "read" notification (2 blue checkmarks in the original app)?
How do I differentiate between sent, received and read? I can't remember having seen those statuses reflected in the status bar.