(This could be an endlessly continuing list. The app really is rough. How many folks can be working on this? It's shareware quality as a mail handler. Does lots of stuff, but as a mail handler, not too good.)

I really like plain text email. I like to send it and receive it. Outlook 2011's (Mac, natch) handling of plain text is horrendous. Very second class citizen.

I'm going to cheat and paste the feedback I just sent in to save time. I'll pretend one of the three guys they have on the mail client will listen. Hopefully so...

Three items:

1.) Need to have Outlook stop stripping out spaces when I paste. Two spaces in a row become one, and indented text, like code, is left justified after a paste. That's simply incorrect behavior.

2.) Need an option to stop wrapping text by default. I don't necessarily want a fixed width message when editing in plain-text format. Same issue described here.

3.) Need to have autocorrect stop inserting non-ASCII characters in plain text edit mode. For instance, an ASCII "..." becomes an ellipses single-character, which isn't expected behavior for "plain text".
In other news, if you add a file called userContent.css to ~/Library/Application Support/Camino/chrome and paste in the following, you get monospaced display of mail in Gmail online (in Camino, duh). Looks like it only does plain text emails in monospace, so that's a win.
div.ii.gt {
 font-family: monospace;
 font-size: 90%;