If you want to make any SIP calls then STAY AWAY from N900. Sip calls are quite choppy with N900. Moreover it doesnt work well with Freeswitch server too.

Since meego uses the same codebase of telepathy and pulseaudio as Maemo, it will be broken there too. Nokia and Collabora need to get their act together to get a working sip on N900/Meego devices.