What i dislike in both YAM (beta) and SimpleMail, is that they are both damn slooow and their window layout is not very optimal for a 800x600 (or less) screen.
What? I use YAM in 660x436 and I don't see how the window layout could be any better.
YAM is probably the only Amiga program I have that I don't need any updates for. It has no annoying bugs or things I want fixed. (HTML emails can be easily directed to IBrowse and I don't see any need for composing HTML emails)
Edit: Oh, I see you said YAM beta. There's a 2.5 beta? Has the layout or speed gotten worse? If so, just use 2.4 p1.