I've been teaching for 20 years. I've been a Mac user for even longer. I hate paperwork and do everything electronically as much as possible. This makes me heavily reliant on my MacBook Pro. Over the last few years, I've looked for iPad-based apps for teachers. My conclusion... they are all crap.
IMO, the fundamental problem is the import/export limitations of the iPad. Any app that has a hope of being helpful to me must interface somehow with my district's network and SIS system. Importing student information is a breeze on a MacBook Pro, but doing so on an iPad is a nightmare. Even typing into the iPad is clumsy. Moreover, getting data OUT of the iPad is problematic, especially if using a niche app with limited formatting options.
What I'd like to see is an iOS version of Easy Grade Pro with cloud syncing to EGP on my "real" computer. This would enable easy input of homework grades as I walk around the classroom. That would be about the only scenario where I picture an iPad to be a useful class management tool.