Update: The "Multiple-account support" section has been rewritten to correct my original misunderstanding of how it works.
The new version of Tweetdeck is out, a bit ahead of schedule. (You can also download Tweetdeck from Download.com.) , this version adds cloud synchronization and other features. But I found the implementation rough in spots. Here's a quick hands-on overview of the main new features:
Synchronization: The big feature: searches and groups are saved to your online Tweetdeck account, and setting up the account is easy. Now when you launch Tweetdeck on another computer these searches and groups will be there waiting for you. The interface for managing these is very bare-bones, however. There's no easy-to-view window of your saves searches, for example. You can see the queries you've saved in a drop-down list when you open the search box, but it'd be better if there were more management tools for people who create a lot of queries.
All searches and groups are automatically saved to the Tweetdeck server if you have an account, and of course they have to be synchronized before you can use them on another comptuer. You can't control when your items sync (it seems to be every few minutes), and if you delete an item permanently before it syncs, you'll lose it. You will get a warning first, though, advising you to wait a few minutes before you delete.
Multiple-account support: The good news is that it's really easy to tweet to one or multiple accounts from the input box. You just click on the accounts you want to send from. Easy.
But a key element of the the interface, selecting which account you want to use when you create a new column to view, is initially confusing -- even though it will likely do the right thing for most users. If you want to add a new Friends, Mentions, or Directs column to your Tweetdeck window and you have multiple Twitter accounts in Tweetdeck, it will ask you which account your want the column to be for when you try to add it. If there's only one account option that makes sense for your choice -- if you have two Twitter accounts in Tweetdeck and you already have one Friends column showing and try to add a second, for example -- Tweetdeck will just automatically select the account that isn't displayed. This is probably what you want, but in my case, on a Tweetdeck installation with a lot of columns configured, not all of which were showing on the monitor, I got confused because the app seemed to be making a choice for me that wasn't what I thought I wanted. Turns out, it was.
In the original version of this review I criticized Tweetdeck for having an opaque method of selecting accounts to display, but Tweetdeck is actually much smarter than I first gave it credit for -- if still less than obvious.
Reply options: : There are some cool new activities you can take on each tweet you see. A "reply all" option creates a message that includes the @ addresses of everyone mentioned in a message. You can also block users, report spammers, follow and unfollow, and add users to groups directly from their tweets. These features will make power Twitterers happy.