I've tried toodledo (both the app and the website). I've since migrated to the native iPhone app.

I liked toodledo for the fact that you could email tasks to certain lists. I did not like the fact that I could not see an archive of my completed tasks. This was especially true for projects. I like to have the option of reviewing my accomplishments over the course of the year. That said both the app and the website worked just fine. No desktop app though.

What I really like about the iPhone Reminders app is that you can see those completed tasks. Works very well (obviously) on the iOS devices. The website via iCould works well enough. It is somewhat clunky, but not too bad once you get used to it. Another obvious note is the great sync between iOS devices if you have more than one. You can also share tasks or lists with others.

Where I've "solved" the desktop app issue is one of two ways:
1. I simply keep a browser window open to the reminders site and enter as needed
2. I have an iPad and find that task entry via that route is really quick

All in all, it's really a matter of preference more than anything. I went "native" due to ease, sync, stability and archive records. I do miss the email option of Toodledo, but not enough to make me go back (it was nice when in outlook to simply create a quick email and send to a given context list).

Hope that helps.

Oh yeah, it is nice that the iOS app is free too!