Contrary to the article http://rememberthemilk.com does support multiple lists (I currently have a dozen or so).

I've been trying RTM for a few weeks and my biggest cons are:

1. the mobile clients are hobbled. The wife and I Use the android and iOS apps and constantly feel like common things are difficult and uncommon things are impossible. You cannot creat a new list from the app, for instance.

2. Poor support for batch operations. This is especially true on the mobile app. The only batch operation is "complete/uncomplete".

The two big Pros: 1. There is an iOS and an android client

2. There is support for sharing lists between accounts.