6wunderkinder, the company behind the popular Wunderlist to-do app, has just launched a sequel to that fantastic app that works across iPhone, Android, Web, Windows, and Mac platforms and features a refreshed design.

Although there are some other great to-do list apps out there, namely Clear, Any.Do, Astrid, and Remember the Milk, Wunderlist has been own of my personal favorites because it works well across every device I own. But it’s always had a few missing features. Notably, the app didn’t have recurring tasks, which are useful when you have a task you need to do daily or weekly, and doesn’t have calendar syncing with services like Google.

Christian Reber, founder and CEO of 6wunderkinder, told me via email that his team worked on the new Wunderlist apps on all platforms for six months and completely rebuilt them from scratch. The app performance will probably be the most substantial change users will notice.

“The most substantial changes are all technical,” Reber said. “Anyone who builds native apps, knows how much work it is to build just one app. We’ve done that with five — and we are launching all at the same time. This has been a huge and tough challenge, and I’m so happy we’ve made just in time for Christmas.”

Reber believes experienced Wunderlist users will appreciate the changes and thinks it could attract new people to the fold.

“The biggest changes for the users are at first: new beautiful and rock-solid apps,” Reber said. “Everyone who used Wunderlist 1 on a regular basis, will notice a massive change in quality. We’ve also put in new features, starting with ‘our users’ most wanted,’ like Reminders, Subtasks, and Recurring Tasks. But the most important difference for all users will be the Activity Center. It helps users to stay connected while working collaboratively on lists and tasks. It tells you what everyone is working on. It may seem small, but if you use it with others, you quickly notice that you haven’t felt like this before about a similar product.”

While Wunderlist 2 does not feature calendar syncing (the only thing I want now!), Reber says it is “on our product roadmap for early 2013.” The company will also work to push out apps for various tablets and other platforms in 2013.

On the pricing front, Wunderlist will remain a free service. But Reber said the company will introduce paid premium accounts in 2013 with a yearly or monthly subscription fee. Exact pricing and feature will come in early 2013.

Check out the video below for more on Wunderlist 2:

Photo via 6wunderkinder