I had tried SP 3 for a very short time, then discovered that SP 4 has several features I need and like, and am now trying SP 4. I am by no means an expert, but I do have an observation and a suggestion for consideration.
Usually I go to the accounts listing and scroll to the Run Account Link in order to go to a particular site and to automatically log in. If this use is usual for others, then I think it might be worthwhile to allow a single click on the account name which would take you to the site and log you in, just as what happens when you click on the "Run Account Link".
I have a sense that it would be faster and easier to simply click the Account Name rather than scroll over to the menu items next to the account name and then to the "Run Account Link" item.