RPLUSJ  Twitterrific is an excellent desktop solution for Twitter, especially for users who are looking for a minimalistic user-interface and have no desire to spend hours every day organizing follower groups or engaging in endless back-and-forth conversations.

If your workflow is like mine, you simply want to get your updates quickly and post a Tweet with as little hassle - and in as few key strokes - as possible. Twitterrific does this with a simple keyboard shortcut. It's easy on the eyes, well designed from a UI point of view, and is light on resources.

Sadly, the Mac version is being neglected by the developers and is lacking at least one useful feature for "speed" users, like myself... a retweet shortcut. Search would be a nice addition, too.

If you don't want to pay to register the app, Pwitter is a similar, free program, albeit not quite as pretty.  
(Version 3.2)

PENGUIRL  Twitterific for Mac seems to have stagnated as all efforts appear to be focused on Twitterific for iPhone. If the Mac version had the features of the iPhone version that would be great.  
(Version 3.2)

FANCHEE  I agree with many people here saying Twitterrific for mac seems to have fallen well behind, due to the efforts placed on the iphone app.

I got Twitterrific for free in the macheist nanobundle. It was my first desktop twitter app, so keep that in mind. Because at first, I thought it was fantastic. I liked the growl notifications, I liked the menubar icon with no dock icon forced upon me, and it was easy to tweet and reply to tweets. And I really liked the notification sound of the bird chirping, cute! So it led me to download the free iphone app.

What a huge difference! So much more functionality to the iphone app. Which then led me to explore other desktop twitter apps with more functionality.

I ended up with Tweetie and now Socialite. What I love about Tweetie is I can click on a user and really dig into that user's info, such as tweets, mentions, and most importantly to me, their user info (location, website, bio, etc) No easy way to do that on the desktop app for Twitterrific. Sure, you can on the iphone version!

Twitterrific and Tweetie use about the same amount of system resources, which is very low, so that to me was a non-issue. Tweetie doesn't allow me (that I know of) to hide the dock icon and I'm not a big fan of this.

Overall, after checking out the competition, I am disappointed in the Twitterrific desktop app. Once it catches up to its iPhone counterpart, it will be great. Until then, I'll stick with Tweetie and even Socialite.  
(Version 3.2.1)

FREVOI  During the next week, you can get it for free at http://www.macheist.com - If this is considered spam, please delete it, but I think that this is a really good tip. ;)  
(Version 3.2.1)

LANDI TRANCE  Twitterrific is the best i like it .  
(Version 3.2)

FROMAGE-HEAD  Configure to quit ?  
(Version 3.2)

GCOGHILL  I was hoping for a beefier feature list for this update. I like Twitterific (tried the rest, keep coming back) but it desperately needs a way to separately view Direct Messages and Replies (tabs, or whatever).

Including a URL shortener (choice of multiple services with account linking would be nice) is also something I would like to see, but not on the top of the list.

And while I am on the feature request soapbox, I'd also like to see an option to open links in the background, an "unread" count in the "title bar" (or whatever that top portion is on an HUD window). A pref to prune read tweets after X hours/days. And a pref to allow clicking of the Growl alerts to jump to the respective Tweet.

Some sort of Groups feature would be nice as well.

I did contact the devs a while back and was told that many of these were on the list for future updates, but was not given any sort of timeframe.  
(Version 3.2)

PENGUIRL  This update address' my primary complaint, which was all messages being marked unread upon launch. The addition of https communication is long overdue but finally included. It's the best Twitter desktop app for Tiger, and possibly OS X. My only complaint is that it is overpriced, really it shouldn't cost more than $10. If the ability to manage your Twitter account were included it would be worth it's current price.  
(Version 3.2)

MARTIN PALJAK  If you're a casual user of online services (which twitter users often are), do not use this. It's a software you have to pay for, which in its default configuration sends your twitter password over the wire in PLAINTEXT which means every schoolboy with a laptop can sniff your twitter password in a public hotspot. Without manual command line configuration (hey! this is mac, not linux) you can't change this insecure behavior, which is not acceptable in 2009. A new software where this should have been fixed has not been published in almost a year. In the light of recent twitter "password problems" I would actually stay away from twitter or at least 3rd party applications anyway.  
(Version 3.1)

YOSHINATSU  I actually have had a really nice experience with Twitterrific, I don't even GET why Tweetie became so popular all of a sudden.  
(Version 3.2)