“Member blogs come up, but each new member would have to configure their own widgets.
I’d like members to be able to join and have everything set up for them. “
this comes up under basic WPMU blog defaults, and is covered extensively over in that forum. there’s even 2 plugins available to set blog defaults.
with widgets it’s a little different – if you don’t want them to change anything, don’t use widgets. hardcode it in the theme sidebar.