Thought of the Day - Online To Do List Roundup

A while back i blogged about my love of To Do Lists and at the time i was enamoured with Ta-da Lists by 37 Signals. While it is beautifully simple and totally fulfils their vision of; "competing with a Post-It note", i started to yearn for something with more control and flexibility. So over the last couple of months i have been moving between various webapps for capturing To Do's. I don't think i have yet found the ideal webapp (and it might not exist) but i thought i would share my experience with each of the sites so hopefully other people can find the perfect To Do List for them.

Ta-da Lists
Despite my quest to find the perfect mix of features, i still use this on a fairly regular basis, its great for short ad hoc lists and capturing things to be done quickly. I even sometimes transfer To Do's from other sites into this for the satisfaction of ticking them. Superb for short ad hoc lists, not so good for more complicated projects.
Pro's: Beautifully simple, replaces Post It notes, quick and intuitive to use, satisfying animation when tasks are complete.
Con's: Can't arrange your high level lists, no support for rearranging tasks between lists, not hierarchical, does not support; tagging, reminders, due dates, searching.

Remember The Milk
So from Ta-da Lists i briefly moved on to Remember The Milk after reading a great article on how to use RTM with Getting Things Done. It has support for tagging, reminders, multiple categories of lists and even setting locations with google maps. I think in principle it could be great but i find there are some interfaces niggles that annoy me.
Pro's: Very clean looking interface, works offline with google gears, support for; tagging, reminders, due dates, prioritisation and reordering of tasks, physical locations for tasks.
Con's: Can't reorder your high level lists, not hierarchical, interface doesn't quite work for me (rollovers don't stick), clicking anywhere on a task marks it as complete, slightly silly name.

Treedolist
I had a few annoyances with the user interface of RTM and it didn't offer what i really wanted; a hierarchical task list. I worked in project management for a bit so i like the idea of having subtasks that all contribute to a high level task and i hadn't found that in any of the other webapps. While it is possible to do this in Ta-da and RTM it is only to one level i.e. you have a list composed of tasks, but you can't have subtasks within each task. A google search for "hierarchical to do list" lead me Treedolist which is specifically designed to be hierarchical (like a tree).
Pro's: Hierarchical, intelligent search bar, support for; notes, links, due dates, virtual tagging (if combined with search), changing font sizes.
Con's: Visually it is rather ugly, the interface is quite clunky (old fashioned and unintuitive), you can't reorder tasks other than to the top of the list or to become subtasks, there are some inconsistencies with keyboard shortcuts and actions (sometimes they work sometimes they don't).

Backpack
I had looked at Backpack a while back but i dismissed it as some sorta weird replacement for a company intranet, but after reading Getting Real (great book - notes to follow) it seemed like it might do what i wanted too. Overall there are a raft of features that i have no need for (newsroom, writeboard, journal etc) but the Pages (and if i paid for it, the Calendar too) are excellent. The Pages in particular are really flexible, not only can you have multiple lists on each page, you can split them with dividers, add notes sections and even writeboards. Alas you are limited to 5 pages on the free account which is workable but not ideal.
Pro's: Great interface, easy to move tasks between pages/lists, best visual layout method i've seen (lists, dividers, notes, writeboards etc), the same satisfying animation as TaDa Lists when you complete a task.
Con's: Can't reorder pages (only alphabetically), very limited number of pages on free account, no support for; due dates, task level tagging, assigning notes/links to individual tasks.

Todoist
I literally just stumbled on this tool while writing this post during random googling for links and it seems to be just what i'm looking for. If it works out i will do a longer review of it later, but here are some initial observations.
Pro's: Great interface, hierarchical tasks AND projects, ability to reorder tasks and projects, due dates, multiple projects, easy to move tasks within lists and between projects, prioritisation/reordering of projects.
Con's: Slightly strange query system (it might search?), the page is too wide for my 7" EEE, i haven't used it in anger yet.

Some other resources:
Top 10 Web To Do Lists
LifeHacker Poll Of Top 10 Web To Do Lists
LifeHacker To Do List Tips
Information on the 'Getting Things Done' System

I should start a new trend; Blogging As A Problem Solving Tool, by researching and writing about your problem you may find a solution to it. Alas i have been here before, i think all of the above To Do Lists have seemed like the answer to my prayers at one stage or another and after extended use i have found little annoying niggles with them. So hopefully Todoist will work as well as it seems to, but time will tell.