The lettering in nokia messenger, while adequate for reading mail, is to small and tight for writing, as the spelling mistakes (which on a phone key pad are not few) are hard to notice, the editing is hard especially when editing letter combinations such as li since it is hard to position the caret exactly between the letters. The caret, btw, is kind of hard to find on the screen sometimes.
I would really LOVE it if I were able to type my messages in the very, very good S60 environment like I normally do. For now, I have two redundant systems, as I like to use Nokia messenger for most of my e+mail needs, but like to use Nokia e+mail for typing longer mails, as it is much easier to use and see.