Well, I'm using the the paid Remember the Milk app, despite the RTM guys being, ahem, spoiled wankers who insist you use their app the way they envision rather than the way you really want to.
Example: the RTM app has two alert sounds: a cowbell and a "moo." You can pick one or the other, but not any of the sounds you may have on your droid.
Another example: there's just one text size, and the text is black on a white background. There's no theming.
More examples: there's just one widget size, there's no way to easily pick dates like "Tomorrow" and "April 25th" from the edit task screen without changing "date modes" with an extra two taps, I don't know how to view notes associated with a task, and that's just off the top of my head.
However, ToodleTo doesn't let you pick what tasks (or group of tasks) can get exported to an iCal calender feed, which means EVERYTHING winds up on your Google Calendar instead of just those tasks you tag "calender" (or whatever).
I've pointed out numerous repeatable and demonstratable bugs with their website, ical feeds, and even one with the Android app and have never gotten a reply.
So why do I use it still? Because it is good enough, supports enough tagging to allow for a good GTD system, and it syncs between the desktop and the handheld promptly and properly, and the multiple iCal feeds let me have multiple Google Calendars (like one for Work, one for Home, and one for Clients). I kind of hate financially supporting these guys, but there just isn't anything better.
-Warr