These may have been mentioned by other people, but here goes:
"Remember my Userid" feature for logging in - it remembers your userid, but does not turn the "remember me" checkbox on! So when you log on next time, the system records that you do not want your userid remembered in future. So the next time you visit SDN, you are not remembered at the login screen!
Scrollbars on right side of screen do not reset - let's say I am viewing a long discussion list, at the botoom I click a link to see the next screen of discussions. The new list appears, but my scrollbar stays where it was for the first list, sometimes resulting in a blank page until I manually scroll back to the top.
Discussion topics titles are too short - I cannot work with a list of topics that look like this:
"How do I...ry?"
and so on. The topic title length must be longer in the discussion list. The tooltip for this field just shows a date and time - perhaps it could show the full title?
I want to see 50 topics at a time (even this is too little now that there are over 100 posts per forum), but the default is still 5. I want to change my defaults and have them saved in my profile, rather than changing them every time.