Before I start, let me emphasize I'm not normally the type to interact with fictional internet characters, but I've got to say I've been 'having a relationship' with Sandy for a few weeks and it's going extremely well.
Next, just in case my wife is reading and before you start thinking I'm crazy I'd better introduce Sandy. Sandy is the internet equivalent of a personal assistant who helps you manage your appointments and to-dos (tasks). Like many people I've tried, had honeymoons with, and divorced many task management systems over the years. I had resorted back to paper and pen before finding Sandy.
To give you a bit more detail, you interact with Sandy as you would a regular personal assistant (not that I'd know). For example, sending a simple message, 'Remind me to RSVP for company Christmas party on Friday at 10am' will instruct Sandy to do exactly that. You'll get an summary of your daily to-do's every morning and a reminder 15 minutes before each appointment. You'll find you'll have instantly have mastered the basics and be looking at some of the other things you can do. There are tips for additional things to do in each mail and if you forget, just send a mail saying 'help'.
Sandy also has a great sense of humor, finishing off mails with catchy lines like 'sharp pencils, sharp mind'. I was suprised to receive a reply to one mail I sent at 2.30am saying 'You're up late, Andrew!'. This demonstrates the thinking that has really gone into the program done by a company called Values of n.
So why is Sandy so good? Firstly, you can do everything by email, including deleting and re-scheduling. Even though there is a nice web interface, you'll find that you very rarely need to visit it. And of course email is ubiquitous so I can easily interact with Sandy from my Windows Mobile phone. Secondly, the usability is amazing. You really don't have to think much about how to work with Sandy. Thirdly, Sandy is incredibly powerful. Even people who have ready books like Getting Things Done on how to manage to-dos will likely not finding missing features. (You can tag requests by adding @category at the end of the sentence). Finally, and most importantly, it works. I'm finding that I'm continuing to use Sandy without any hesitation and she is helping increase my productivity. I can honestly say I've never felt quite the same about a web application.
Huge kudos to the Values of n team for coming up with such a usable application. I would be surprised if this doesn't become very popular and/or mark the start of a new trend toward more usebale web applications. When you starting worrying about whether you have to say 'hi' or 'thanks' when interacting with a web application you know that it must be something different from the rest.