Suggestions

Multiple blocks

Provide intergration for something like Bean which will allow users to create multiple different blocks rather than being limited to just a single block.

Alternatively, give users the an admin screen where they can define how many different blocks are available in the blocks interface (can't remember the module that did this, but Bean would be a better way).

Additional display options

Ability to show the timestamp by each tweet.

Allow user to select between a profile tweet block or search for a hashtag/mention

At the moment the block allows you to view tweets from a certain user. Would be good if the user had the option to show tweets with certain keywords/hashtags which can also be used for displaying mentions.