I think the portable version of Task Coach on folders on various computers synced with SugarSync has all advantages of remember the milk, which is a very good online task manager, but is not so well structured than Task Coach. The main advantage of RTM is the Web-Syncronizing of tasks, a feature which you also can get with Task Coach combined with SugarSync:
Since Oct.2010 SugarSync has enlarged the free storage to 5 GB at the beginning and you can sync an unlimited number of devices (instead of max.2 until Oct.2010)
You can download and registrate SugarSync with these improved conditions from http://bit.ly/bxgp6f or http://2.ly/d7pr .
The useful features of SugarSync for all persons, who prefer to use portable apps, you see on http://www.sugarsync.com/products/ .