I love my N810 sound quality and loud.

Raspberry Pi is a nice device, I use it a lot, but my main phone device is a N900. It will remains for a while yet, even if I already have other phones (mainly a cheap Samsung).

I write/program a lot, then I must have a good qwerty physical keyboard on my phone.

Frankly I do not see reason to have maemo on other devices, to me it is perfect just on phones.
E.g. Pi has a pure debian OS that works great, maemo will not be a real plus on Pi.

Off topic, I share some Pi uses: I use Pi as rsync server between my phones, FTP sync and remote storage, house alarm, presence control, remote switch, remote camera. It provides a VPN wifi too.