I purchased Resolver One months ago and am very happy with it. Think of it as Microsoft Excel but with Python for macros instead of VBA. If you are a veteran spreadsheet user that uses spreadsheets often and you would rather learn/use Python instead of VBA, I would say don't hesitate to purchase it.
As for using it to learn Python, not sure it would be good, but it definitely wouldn't be harmful in any way. You would basically be able to start off python by writing short macros. This would teach you to import modules, use functions, and learn the Python native data types. It would not be a good introduction to object oriented programming or such intermediate topics.