The differences are there; superficially, all clients display tweets in a timeline, and provide the functionality that Twitter.com does. The differences abound, though. Check out http://shawnblanc.net/2011/04/tweetbot-review/ for more.
I see some minor differences, but I don't think they're good ones. It's not just the timeline, the search screen is almost identical, etc, etc. I don't think there's enough here for non-echo chamber users.
I don't know what the name of the Tapbots style is, but it's a little heavy for my tastes.
On the plus side, it definitely has more personality than the official client (which has lost personality over time -- though the iPad app is pure genius), but the UI/UX is over done, IMHO.
