It is a universal app which works on iPhone and iPad. No silly monthly fee!!!
And it does what Astrid did, but better...

I used to like Astrid despite the silly messages, but they rather stuffed up the most recent (3.0) upgrade in a way that lost data for some people, added ads, and worst of all gave the impression that peoples' tasks were being held hostage and the upgrade was being forced! That last part wasn't really the case, but for me the added ads and mishandling have lost them a <3 here and a few *s in the marketplace. Oh well. I'll be investigating Google Tasks tools as an alternative for now (also because I've never liked RTM's web interface: Tasque makes that part palatable for us Linux users though!)

Todoroo's own take on the recent kerfuffle: http://blog.todoroo.com/astrid-3-0-6-clears-up-confusion/

I am one of those people who doesn't like Remember The Milk. I know it's a great tool for a lot of people, but for me, I end up spending too much time fussing with the system, instead of doing to things I'm using the system to keep track of. I need a tool that's as complex as it needs to be and as simple as I can get away with. Astrid fits this bill.
Astrid is not really like RTM, although it backs up to/syncs with an RTM account if you want. If you use RTM, you'll find some familiar features (tagging, importance, etc.) but it's a much simpler, nimbler system, which for me, makes it much more likely to capture todos as they come up.
Astrid also gently nags and reminds you of your todos until you feel silly for putting them off and just do them. Read that last sentence one more time and consider how completely amazing that one small detail about Astrid is.
I use this everyday on my Android phone. It keeps all my personal, work, and college todos with ease and actually helps me check them off instead of just storing them for me to ignore later.
I could not be more in love with Astrid.