I love this so far, but it still needs some work IMHO:

Email message fonts look good on my laptop, but way too small o my 27" Cinema Display. User needs to be able to configure message and list fonts.

User needs to be able to control if signature is above or below quoted text in replies and forwards. Right now it's above which I think is fairly non-standard (though I have no proof, I just seem to see it the other way most of the time).

Some functions are confusing and really need tooltip/balloon help popups - like, what's the difference between the two identical looking "reply" buttons - the one at the top (next to "i") and the one at the bottom? I think the one at the top uses Facebook, but I'm not sure.

The main four icons (compose, reply, archive, and trash) at the top look like they are from Mac OS 7 days. Why so flat? And we need "reply all" and forward buttons.

Would be nice if it could import accounts from mail.app, and had support for local folders.

The app store version is still 1.3.2. Seems like the developer is not keeping the app store version current.

Open Office and Libre Office can both create a PDF with bookmarks from styled text - a feature that Microsloth has withheld from Mac users even in the most current version of Word 2011. I use this feature and I would find it difficult to give up. But the size of the PDF that Open Office creates is about half of what Libre Office or Neo Office create, without image degradation. I haven't found any settings that affect this, so I still use OO, which is why I can't give this the full five stars. Otherwise it is awesome.