There are only a few features missing in The Bat! relative to competing releases. The biggest shortcoming is The Bat's lack of full HTML support when writing and reading messages.
Other deficiencies include an address book import wizard that saves you the trouble of manually exporting an address book from another client before importing it into The Bat!, color coding capabilities for prioritizing your messages, and customizable toolbars.
Overall, though, The Bat's excellent set of features and extreme ease of use make it an easy recommendation for both novice and expert users alike.
Pros: Excellent feature-set, including the exclusive Mail Ticker; easy to use; inexpensive
Cons: Lacks a few advanced features of competing clients - most notably HTML support
