Twitter client requirements

I want a good Twitter client. Here are the features I would like it to have. App names in parentheses are examples of how I want the feature to work, where necessary.

• Native Mac app
• Growl support
• Quick and easy automatic hiding/revealing on new messages or keystroke  (Twitteriffic)
• Obvious but subtle visual difference between ‘read’ and ‘unread’ messages (Twitteriffic)
• (optionally) tabbed interface, allowing the creation of groups based on various filters; Quick access to create/manage tabs from context menu (e.g. ‘Add user to tab…’
  • Explicitly create groups by specifying a set of users
  • Create ‘groups’ based on conversations – select a tweet from someone to someone, then right-click and choose ‘Create conversation group’ to create a group for messages from either person to the other. (Natsulion, kind of)
  • Create ‘groups’ based on hash tags from people you follow, to keep better track of conversations; automatically append the hashtag to your posts to the group
  • Automatically open ‘conversation’ tabs when DMs are received; if closed, it will re-open when a new DM is received; tabs are per-user (i.e. DMs from two people will show in two tabs) (Twitterfon, kind of)
• Flag specific individuals, keywords, or hashtags to be highlighted with separate colours
• Automatically collapse consecutive tweets beyond a certain threshold (to prevent one person from dominating your twitter stream); easily re-expand for reading. (Mail.app)
• Archive all tweets forever, index with Spotlight
• Assign Twitter users to Address Book entries, for better integration (Adium)
  • ‘Reply via e-mail/IM’ option in context menu
  • Replace Address Book picture with (full-size) Twitter profile image
  • Display real name from AB instead of real name or screen name from Twitter
  • Tag archived tweets with metadata to find via Spotlight
• Themeable but with a simplistic default theme, so that users can control how their tweets look and how much data is shown (Adium)
• Minimalist interface (Twitteriffic) unless themeing allows a complete UI overhaul (Bowtie)
• Drag images into the window to post to TwitPic (opens a new dialog to scale image and provide text) (TwitterFon)
• Drag URLs into the window to post in a tweet (shortening with one of the many URL-shortening services out there)
• Parse out shortened URLs, and pull metadata from known sites into a preview (YouTube clip headline/thumbnail, Flickr thumbnail, website title, etc.) (Linkinus)
• Register a URL schema (e.g. twitteriffic://) to create a bookmarklet that posts a URL via the app (most iPhone twitter apps)
• Remappable keys, including Twitteriffic defaults
• Adium/iChat/Facebook/etc. integration (update status on tweet) (Twitteriffic)
• Sync between two Macs using the same account, so that you can see all tweets you missed from wherever you last left off on your other Mac (e.g. when going from home to work)
• ‘Stash’ messages for later review (different from adding a favourite) optionally via Instapaper (Instapaper)
• Bonjour-based microblogging support (to post/receive tweets via Bonjour to people on your LAN)
• Laconi.ca (identi.ca) integration (Twhirl)
• Allow you to type past the 40-character limit, then go back and edit to fit (most well-designed Twitter clients)
• Automatic expansion of the input box to see your whole tweet while typing

I think adding these features, along with a Mac-like look-and-feel, would create the ‘ultimate’ Twitter client. So why am I listing them here, instead of saving it up and doing it myself? Partly because I’m lazy; I don’t care how I get this app, I just want to have it. If I end up having to write it myself, then that’s fine; if someone writes it for me, I’ll pay for it.

What do you think? What must-have Twitter client features can you not live without? Which of my features are garbage and have no place in a Twitter client?