I personally love ZenBe. It is simple to make multiple lists, arrange the order of the lists and everything in the lists. You can sign up for a free account on their website and sync your lists back and forth between your iphone/itouch and the web version. I got it when it was free, but it is only $2.99 and I think well worth it.
To sort the lists you do need to hit edit and then the move items up or down like you when you organize your Favorites in your phone book. There is no 1, 2 or 3 on priority list but for me, as long as I see an ordered list, I am fine with that.
I have a friend that uses OmniFocus and it is an amazing app but it costs $19.99 and is WAY to intensive for me. it did have some nice features like being able to show you what you can work on based on where you are. You can geotag where work is, home, the mall or anything and then when you are in that location, it will show you what can be done based on your location. Cool idea, but way too intensive for me.
Hope this helped. Personally, I wish all apps would have a trial period. Something like 2 days or a couple hours of usage. That way you could actually try an app and if you like it, you are forced to buy it if you want to keep using it. Otherwise, just delete it. I think it would sell a lot more because people wouldn't be afraid of taking a chance on an app and trying it out. I personally would be trying tons of apps which would lead to more purchases, but because I am not made of money, I am hesitant to buy and then try.