I like emailganizer, but since my phone is sync'd up to an exchange server, my email gets setup anyways on the default mail app. There's no way around it.
Also, when I want to quickly send documentation over email (like a picture I took of equipment, a quick voice memo, notes..), I can't do that over emailganizer. Mail app is too integrated and convenient to ignore. I can't just use both (both have their pro's and con's).
The iphone has been the one of the most powerful all-in-one tool I use for work ever. It's a complete shame that it does not have collaspable mailbox. It's also unfortunate, that because of this, I've looked into getting the Nokia Lumia, as I see the Microsoft OS to be superior in nearly every aspect (layout, documents, mail, etc). It's even more suited for my work; especially since we do a lot of RDC, and work in a windows environment. I've seen users interface their Lumias with their work desktop so seamlessly, I'm jealous.