Yes, I have experienced all of these issues since the iOS 6 release. Best bet for now is to just hard close it and restart it. This often happens after a major OS update. I am sure there will be an iOS 6 compatibility release along shortly that should eliminate a lot of these frustrations.
In the mean time, for the not posting portion, for some reason in iOS 6 if your post is not multiple lines, the send button doesn't light up. If you just hit enter to get to the next line, it will allow you to post. So that's at least 1 work around in the interim