You remind yourself to do system backups? What happened to cron, erm launchd? If it's a laptop I recommend you check out Anacron+launchd. (http://members.cox.net/18james/anacron-tiger.html) Maybe rsync? I recently grabbed a 20g StrongSpace account for offsite rsyncs - highly recommended... now if Apple will just fix the -E bug :) (What I mean is if the data you backup uses resource forks, forget about 10.4.3's rsync for right now). But I digress...

kGTD sure is nice for what it is (applescripts ontop of a larger scope pricey and hefty application) but is largely something I use to map the feature sets that are most important to me so I can give my GTD a diet and invest in CoreData. But until vaporware materializes that doesn't require using such a beast to manage lists, I use kGTD for now. Much like Merlin I've probably tested all the GTD systems on OSX, except I probably use the systems less then he does because I suffer from the finding-the-one-true-system bug that turns me into an avid GTD evangelist and application tester more then just sitting down and usin GTD (I know, it's a big no-no) -- kGTD is an advanced version of what some of us remember from a third party kludge to HogBay Notebook... I don't think there is anyway of pleasing everyone all the time short of writing your own.

For people that want to write their own, ADC has a ToDo CoreData sample application on their website. I invite the roll-your-own mac developers to make a custom shoe. Note I'm not advocating the world needs another GTD system -- I am simply saying, once you've tried them all you'll likely say wouldn't it be nice if I had features from X, Y and Z -- and there's only one path to getting what you want (time-willing).