IMO it's too early to judge Unity's stability. Besides, the feature freeze is on the 24th of February, it means that after one more week of development Unity won't receive any new features and the whole two months left before release the team will only fix bugs. And Unity is based on Docky's core, which is already tested by the time.
We have to choose between gnome-panel,
GNOME Shell, Unity and unstable but promising
Pantheon. We haven't even seen all the features planned for those shells yet (especially Pantheon). Gnome-panel is complex and bloated; it has such long lists of legacy APIs and unresolved bugs, some of them are rather intrusive. Unity is faster than gnome-panel, and makes the whole desktop behave faster.
GNOME 2 menu is awesome and Slingshot is going to continue that idea, that makes it the best launcher available. GNOME Shell has horrible application launcher now, almost as bad as start menu in Windows, even worse in some aspects. I haven't seen the current state of Unity's dash, so I can't say anything about it.