nice to hear that
i'm dealing around with the same problems.

i won't be fixed too much on siverstripe user-rights.
user/group relations aren't useable until there's an easy possibility
to attach users in 'many groups' within the cms.
looking at the end oft this thread show's, that they are 'on the way'
http://www.silverstripe.com/site-builders-forum/flat/3340?start=8
but i didn't see this solution anywhere till now.
(yes i can do that for myself, decorator could add this thing, but why is this no standard?)

and even if things were 'all right' with groups, i think that
separating 'frontend rights' (only members, no cms login)
and 'backend rights' (cms-uesrs) is a good design decision.
so my conclusio is
i use silverstripe groups and rights only for cms
and build my own 'rights' for members that can't login
in the cms by decorating Member with the fields i need.

BTW: would be nice to hear some thoughts from someone oft the silverstripe team,
how they see these things...