To my surprise it is very stable so far. Earlier Gnome Shell versions were not as stable. After installing various extensions (dock especially) it is as usable as Unity for my needs. It seems more responsive as well. I am not really into the Unity new features like HUD. It sounds to me like Ubuntu is making a mistake with Unity compared to Gnome Shell.
To make an old extension support latest Gnome Shell version, it is sometimes necessary to update the extension metadata with what's given by gnome-shell --version. For the weather extension you can just edit using gedit:
sudo gedit /firstname.lastname@example.org/metadata.json