To crosspost to Twitter from Netbot for iPhone, just tap on the Navbar in the Post window. On Netbot for iPad, tap on your Avatar.
I get why a lot of people will be happy about this, but to me this is the fundamental flaw facing App.net. Most people simply do not have the bandwidth to keep up with Twitter and App.net (I don’t), so why would you use both services? Crossposting is something I hate and I really think is bad for the overall health of both Twitter and App.net.
To me, cross posting is like that person that calls you, leaves a voicemail, and then texts you the same thing they just left your a voicemail about. That is to say: annoying.