You would be better off with a Google Nexus S or Galaxy Nexus IMHO. Even a Motorola. Android works on the N9, but is far from usable for an everyday phone. If you want Android, get an Android phone. If you want Tizen, get a Tizen phone (if a Tizen phone ever should be produced). If you want Harmattan, get the N9.
You never stated what kind of developer you are. That would help. But will say, to be honest I'd go Android instead unless you're married to Qt.