Unfortunately dude not all apps have portrait abiity themselves...some apps just fit in. What the CSSU is doing is twicking the UI of the Hildon Desktop for portrait, not individual apps..so unless the apps themselves have portrait capability you are not going to get the full picture on portrait. Oddly some things that work well on portrait but arent meant to is the contacts app and the notepad...lol However the media player is best on landscape.

You could get the conversations to work in portrait via a bit of modding. Google conversations mod for nokia n900. And remember after the mod you must have cssu force all aplications to rotate option on or else it will not rotate the mod just allows the UI to fit in the screen when in portrait does not rotate it, Also you will need a portrait keyboard my preference is the fast sms one from the repos. cheers