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Full user review
"Good way to manage twitter"
Columns help organize friends by interest, good integration with related services (ie image hosts, link shorteners, etc.), lots of features.
Acts oddly when left open awhile. Disabled support for real columns. Manual API settings are meaningless if you have old-style columns around still.
I've tried other Twitter clients, but TweetDeck is the only one that offers the feature set that it does in combination with pretty great columns (caveat, which I'll address in a bit).
Scheduled tweets, link shorteners, hashtag remembering, drag-in image uploading, and a load of other features I'm forgetting about or don't really use myself.
(Aforementioned caveat) Columns used to be much more useful than they are now. Now, they're just a reflection of the Groups/Lists that you have on twitter. Before, they were custom and local so if a tweet was in All Mentions and it got marked as read in a column you created called Noisy, it would be marked read in All Mentions and cleared out the next time you hit the Clear Seen Updates button.
Besides being a great way to manage information overload, it also let you read all the tweets from people interested in one subject in one go and then move onto the next subject.
If the new Columns would operate on that same concept, they'd be fine. Instead, a tweet marked read in Writers, for example, doesn't touch its mate in All Mentions.
In addition, I don't like tweets coming in so fast that I can't read the tweets I'm looking at so I set custom API. Every time it's supposed to hit API, it hits it once for every one of the old columns I haven't deleted yet. It seems to do this at about ten second intervals and is really inconvenient.
Bug reports have been filed on these complaints but in the case of bringing back the old columns, TweetDeck is uninterested. For making the Mark Read button work across columns, they seemed somewhat less disinterested, but still in no hurry. For the API issue, I'm not sure if they plan on addressing that or not.
I realize this sounds like an awful lot of complaining, but TweetDeck really is the best Twitter client I've used. It's a testament to how much I love this software that I keep using it despite these issues.