These were not intentional omissions. 3.0 was a complete rewrite and there are still many features that we know we need to add in order to be on par with the web experience.

I strongly encourage any users with feedback or feature requests to hit up my ask box: http://blog.bryanirace.com/ask. We really are listening and plan on providing the best mobile Tumblr experience we possibly can.

Edit: Worth noting that we added post sharing options in 3.1 (long press on the 'Like' button).