It is my opinion that the free version (the Freemium version) offers every feature you'll need to evaluate Watson. Frankly, the personal edition doesn't add enough (per file limits can be overcome programmatically externally to Watson and with some simple space used administration) so I'd recommend that when you are ready to upgrade, you go for the professional version. What really adds value is the additional data source support, the multiuser environment, and the ability to share (data sets, refined data sets, explorations, predictions, and views). In the next chapter, we will walk through the upgrade process (from the free version to the professional version) and explore some of the features found only in that (the professional) version.