The Add Account screen has its own close button, and Esc closes the account picker. Shipped in 1.1.0.
Settings › General › Inbox › Open to: the tab you used last, All, Primary, Updates or Promos. Shipped in 1.3.0.
Signatures and lines like "Sent from my iPhone" tuck under the ••• button with the quoted history, whichever app the sender uses. Replies from Canary no longer repeat the previous message. Shipped in 1.3.0.
Accounts, signatures, templates, rules and settings stay the same on all your Macs. Mail and passwords never leave each Mac. Shipped in 1.2.0.
Conversation summaries and suggested replies can be switched off separately in Settings › General. Shipped in 1.2.0.
Hover a sender's name for their address, copy it from the menu, or show addresses right in the list. Shipped in 1.2.0.
Send Again (⇧⌘D) opens any sent message as a new one with the same recipients, text and attachments. Shipped in 1.2.0.
Format your signature with the rich editor, or paste or import your own HTML, with a live preview of what recipients see. Shipped in 1.2.0.
Pressing ⌫ or Delete asks first; deleting from Trash removes mail for good. Turn the prompt off with "Don't ask again" and back on in Settings › General. Shipped in 1.2.0.
Activate with a key or an emailed link, restore with a code sent to your purchase address, and use it on up to 3 Macs. Licences are signed and work offline. Shipped in 0.6.