1) Having a look at the upcoming openSUSE 10.2 we can see some surprises:
They switched to GNOME as the default desktop (it is the the default choice in the selection) and they removed the GNOME top bar and just left the bottom bar in place.
While many GNOME users will probably not like it, SUSE has a strong point here:
All those switchovers from KDE and from Windows are used to dealing with just one bar. It is the first sight that matters if you feel comfortable with an OS or not. This will attract novice Linux/Gnome users, while experienced Gnome users will know how to enable the second bar with just a few clicks (so they would not suffer from this move).
I think it is a wise move that Mint should consider for its distribution as well.
2) Why don't you use the stylized Mint Logo for the start button of the taskbar? The one that is featured here on the top left of the forums? It looks way better than the one presented in the current beta.



