You can download these GIS solutions and trial them on your pc, laptop or tablet. With proprietary software such as ArcGIS and MapInfo you will have a thirty day to sixty day window in which to appraise the software without cost to see if it meets your requirements. Quantum GIS is open source software and as such there is no cost implication or time limit in checking out its features and functionality.
The other factor, which is often the case, is how motivated you are to learn through methods which rely on you persevering to work on your own, over a minimum of six to ten hours, to achieve any level of competency. How often do we start a project, like going regularly to a gym ,only to find that we have neither the time or the interest to continue with it after a couple of weeks? We then end up paying for a gym membership which we don't actually make use of. This can also apply to many other resolutions that we make in good faith and then find,, always through well considered logic, that we no longer wish to pursue.
So, for those who have the motivation and the time, for options such as on-line courses, these methods could offer a way of becoming proficient with a GIS desktop solution. However, if you need to become effective with a GIS, and start to achieve your specific objectives more quickly, then a one or two day face-to-face training course may be more appropriate. Especially if your chosen course provider also offers support in the weeks after completing the training!