I've used gwibber in the past but because it kept crashing on me, I dumped it for twhirl. The new gwibber 2.0 seems to have fixed that issue. At least, I haven't experienced any crashes so far. Your mileage may vary.
So what's new in 2.0? Well the sidebar thing is new. I prefer this sidebar with trees layout compared to the tabs in the old gwibber. I would run out of space for new tabs, and I don't like to scroll horizontally. It just feels more natural to me to scroll vertically.
Another new thing is the search box up top. When you search for something, a new stream appears under 'Search' in the sidebar. You can also drill down to filter the search results by service. I do have a complaint though: searches take a while to load. This is probably because of my ISP more than any fault of gwibber but it is still a bit annoying. Probably related to this bug.
Closing the sub-streams in the sidebar can get a bit frustrating. Either they take their time to go away, or I'm just not clicking at the right spot most of the time. The icon is pretty big. Ctrl-W works fine though. Does this happen to anyone else?
If you're running Ubuntu you can get gwibber 2.0 by going to the gwibber-daily PPA and follow the instructions there.