Just a plug for an app I've been using for over a year and a half on my phone to access my work and google apps mail on Android.
https://play.google.com/store/apps/details?id=com.ninefolders.hd3Its $10, by far the most I've ever spent on a phone app, but its worth it and when I got a new phone and then had it replaced, their customer support reset my license each time so I didn't have to pay to reinstall.
Aside from a clean interface and ease of use, the main reason I got it was to sandbox my mail from the rest of my phone. You can set the security model to work at the Device Level (which is how the built in mail app and the exchange specific app work) or at the Application Level!
I want the Application level for 2 reasons:
1) our exchange policy requires a 4-digit pin or stronger security method to unlock your phone. I like to use the pattern swipe or facial recognition which are not allowed. By opting to use "App level" security, I can use any method I want to unlock my phone (even none) and then just enter a 4-digit pin to access my e-mail app.
2) exchange has the power to wipe your phone data. you can do it yourself through OWA or anyone with access to the exchange server can do it on your behalf. I trust that my company wouldn't wipe my phone -- but, yeah, no I don't like them having that power.