I’ve been using Remember The Milk for a while, and it’s a great tool.  There are two things about it that I don’t like:

1. The horizontally-oriented list tabs.
2. The $25/year pro account.

Fortunately, the first of these can be solved with a browser plug-in.  A Bit Better RTM turns the list tabs into a vertically-oriented list on the left side of the screen and greatly improves the aesthetics of the site, especially if you have more than a handful of project lists.

A Bit Better RTM is available for both Firefox and Chrome.