One of my WP sites requires people to create "subscriber" accounts and login in order to post comments.
One downside is that when you login, you are taken to the site's dashboard page.
With an earlier version of WP, I had manually hacked some of the wp-admin files so that these users would see almost NOTHING on the dashboard page, except the link they needed to view/update their profile and password.
That was 2 or 3 versions ago, and it's a pain in the neck to figure out how to re-do those customizations every time you upgrade.
I just noticed in 2.6.2 (by logging in as a "fake" user with subscriber access only) that it still shows the entire dashboard. Even though there are no "admin" links across the top row, there's still the "right now" the incoming links, recent comments, development blog, etc.
As far as I'm concerned, these are things regular users don't need to see and, frankly, shouldn't be allowed to see. Making matters worse, the one link ordinary "Subscribers" do need, the "Profile" link, is way up in the top-right corner, in a relatively small font, away from the rest of the "action" on this page. While those of us who administrate WP websites know to look there, regular users do not. I've had people e-mail me asking how to change their password.
I think it would be better if only admins got to see the dashboard. Regular users should either be taken directly to their profile page, or right back to the homepage (or whatever page they were on when they clicked the "login" link.