I'm a big user of Google Tasks. It's barebones but I like it mainly because of its integration with GMail & Google Calendar. However, Google doesn't have a mobile-friendly site to use Google Tasks.
Over the weekend, I built Taskyo (http://www.taskyo.com). It is not meant to replace the main Google Tasks site but instead supplement it. This is why the features for Taskyo is limited - no editing of lists, ordering of tasks among others. Being able to create a list, create a task, marking a task as 'Complete' and deleting a task pretty much covers everything you need when accessing it on the go.
I built this using Python on App Engine and JQuery Mobile. It works well on the phone and on the tablet too.
Developing this app also allowed to me play with the new Google APIs for the first time. I really like what Google did. All the APIs are consistent and centralized. There are libraries for Java, Python, and PHP. The API Explorer (https://code.google.com/apis/explorer/) was particularly useful.
I found some hiccups though especially how to do OAuth2. The authorization example they have for Google Tasks (http://code.google.com/apis/tasks/v1/using.html) was not for websites. But having worked on the Twitter & Foursquare API using OAuth2, I eventually figured it out. With the other issues I had, the Google Tasks Developer Forum helped me solved them (http://code.google.com/apis/tasks/forum.html).