Just installed Communities on my E71. A few suggestions:
It feels slow. The UI should be more responsive, even with the cost of the data updates being a bit slower. This is the biggest gripe I have about Communities. It must be more responsive to user interaction.
Twitter tweets are shortened. Please don't. Currently I have to stop at a tweet, then wait one sec for it to show the full text. At the same time it expands the selection, making navigation difficult, as the page contents are shifting. Give me full view of the tweets.
Note: On Facebook I can understand this, as the messages can be very long.
Twitter and Facebook: show more tweets/messages on the same page. 10 or 20.
Twitter needs more functionality: [saved] searches and my lists.