The most important benefit of changing to this widget is that it works! The other widgets yielded spotty results with too many fail whales.
The other obvious benefit is that it allows me to embed many more tweets in my sidebar than the others did – through a scrollable interface.
Performance: Occasionally it doesn’t work. The result, a black fail whale rectangle with nothing in it. While annoying, so far the black rectangle appears less often than the fail whales I experienced with the other Twitter widgets. Also, sometimes the black box turns into the proper widget if you give it long enough. Odd.
Flash: On the downside the widget requires Flash. As a result, it does not work with the iPhone. Note: There is an html version of the widget available – though it’s not as nice or useful.