Whilst watching the partner source CRM 2011 training videos, I was interested to see you can deactivate systems views
you can also copy system views.
Any new feature which is extremely welcome because people used to do it programitcally in CRM 4 is filtered lookups. You can filter lookups using any of the previous views for that entity.
you can watch a youtube video about filtered lookups here
I also found a blog post on it here
To be honest this is one of the more straight forward changes added into CRM 2011 and not one that needs much puzzling over.