As numerous commenters on LH point out there are two obvious omissions from this list "Things" and "OmniFocus".
I personally prefer Things, paired with the desktop client it's easy to use and effective. Out of all the GTD apps it's the one I find I easiest to use daily. It really doesn't get in the way. My only small beef with it is the need to sync over wifi.
I never bought Things - I can't get myself to use productivity applications, they just seem too limiting - but I tried the demo, and it is BEAUTIFUL. I wish all programs had such a gorgeous interface.
i've actually found that a really nice combo would be things for keeping track of dates, and then using evernote to document details + generally store info and more complicated planning elements
I personally prefer Things, paired with the desktop client it's easy to use and effective. Out of all the GTD apps it's the one I find I easiest to use daily. It really doesn't get in the way. My only small beef with it is the need to sync over wifi.