I use Tweetbot and love it. Best Twitter app IMO.
To answer your questions:
- Yes, Tweetbot has its own UI. It's familiar to anyone who's used a twitter app, but has some really nice UI features (customizable tab bar, smart gestures, conversation & reply views etc)
- Is it easier to go way back? No, you need to scroll
Advantages:
- Lists: Tweetbot handles lists really well. You can switch your timeline to a list very quickly and easily (one of its best features if you use lists)
- Conversation/Reply view: swipe right to view a conversation thread or swipe left to see replies (again a great feature to follow conversations)
- Fast: For me, Tweetbot is very fast to load new tweets (definitely faster than the Twitter app)
- Smart gestures: Within a tweet, tap the icon to see details of the tweeter, double tap to see details of the tweet, triple tap to reply/favourite (this is customizable) etc. Also you can tap and hold stuff to get options (e.g. tap and hold a url to open in Safari, send to Instapaper, etc)
Probably best to watch the video:
http://tapbots.com/software/tweetbot/