An undergrad here (Jen Brown - now a TA for CS2803), did a survey of the 2390 class this past winter about Squeak. What they did and didn't like about it, what they'd like to see changed, etc. The Squeak team from Disney was here in April, and she presented her reuslts to them.
Although it hasn't been confirmed, a number of these were implemented in the latest version of Squeak - 2.5. This includes the ability to change window colors, set global colors, etc. Most of these can be seen under the 'preferences' window option. (click in system window, choose 'help', and choose 'preferences').
For an example of this, look at the two system browsers below. The first one is the default:
The second is the one I use whenever I use Squeak. Notice the rounded corners and permanent scrollbars:
