I've just registered and tried Producteev, I think you are in the right direction and I will be able to use it soon, the is just something that in my opinion would be very useful to have (they apply to the iphone app too):
These are the first impressions, I thought it would be useful for you to share them...
For item #5, I could be mistaken, but if you click on the little star it allows you to select a priority.
It's not entirely intuitive (I usually think of stars as yes/no type flags, as they are in GMail), but it appears that is where you can set priority.
I really like #2. I have been having to change my task names to be "Project Name: Task Name" just to be able to read them all.