I'm impressed with their positivity but then they have effectively just been granted a monopoly.
I'm sure they do well, but they definitely don't have a monopoly.
Sources: http://benjaminmayo.co.uk/how-many-people-use-twitter-s-own-...
http://thenextweb.com/twitter/2012/07/23/only-an-estimated-2...
Of course, there's nothing to stop Twitter from creating new new rules that kill Tweetbot or remove the advantage.
What makes you think that?
Twitter didn't set a hard limit of 100K tokens for all new apps. That's just the initial limit. You can request more, and I assume they would grant them to popular, legitimate apps.