ive always used gtask but need a bit more power so i installed nitro on the ubuntu app store and told the software to use ubuntu one for sync support, i could have used drop box if i didnt use ubuntu one.
I installed nitrodroid on the nexus from the google play installer. I again told it use my ubuntu account.
Created a task list on my droid and click sync and added a task on the ubuntu box and got full two way sync
I tried the auto sync on ubuntu but this wasnt good, if i was adding a new task and it started to autosync it closed the current task i was adding !! so i just manually sync. But works great..
Also available for mac – give it a go its great !!