I've been using Tent (https://tent.io) which also adopted 256 characters, and I think it's actually quite generous for statuses. Maybe too much; the nature of microblogging changes when you don't have to be concise. I bet the sweet spot is probably somewhere in 160-200.
Sticking to 140 would be a good standard for a microblogging standard since it would allow you to syndicate out to Twitter and you could emulate the API and automatically have other apps support that character limit.
If you go beyond 140 it is then no longer a microblog post, but rather just an ordinary blog post.
