If you love Things, you just got a whole lot more to love. The folks at Cultured Code have finally added iCal sync, and they've done a spectacular job with it (outdoing, in my opinion, OmniFocus' sync). In the preferences, you can sync just your "Today" tasks, or just your "Next Actions," or you can get crazy with it and assign calendars to different tags, projects or areas of responsibility. This allows for utterly amazing flexibility and an array of possibilities.
The major benefits of having Things synced with iCal all revolve around the tight integration that iCal and Leopard's To Dos have with the rest of OS X. Being able to refine what is actually synced means you have complete control over what you see on an iCal printout or even what you put on a public or shared calendar. To Dos can be delegated, emailed, linked, prioritized and more, and Things is picking up every external change I throw at it.
You can have a calendar that functions as an inbox and use whatever input method you like to get tasks there. The "@" symbol can be used to add tags as well. Moving a task from the inbox calendar to another calendar synchronized with Things will do exactly what you think it will ... move the task to the project or area of responsibility assigned to that calendar.
This also solves my other major problem with Things, no easy way to turn Mail.app messages into tasks. Now, with a right click to make a new To Do you can create a new task in Things that contains a link to the original message. Unfortunately, Mail.app's handling of To Dos is a little buggy in some cases, but that problem is easily taken care of by using MailTags to create the tasks.
The final reason I'm so excited about this new release is that Leopard To Dos are part of an API that all kinds of third-party programs can access, and can therefore integrate with Things now. Anxiety, Out of Mind, Today, MailTags and other little applications we've mentioned can all work in two directions with your task manager.
I'm a little obsessed with Charilaos Skiadas' GTDAlt bundle for TextMate right now (along with piles of Ruby code to extend it), but the new sync feature in Things made it extremely easy to pull my tasks in and take it for another spin. Having sworn off the "pretty" task managers and pledged my allegiance once again to all things plain text, I don't have the heart to change my system again quite yet ... but it's becoming obvious that when Things comes to fruition, it will be a force to be reckoned with. If this was holding you back (like it was me), it might be time to take a look. Things is going to be $49 after release, but you can still get in on it for $39 right now.